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Higher diet quality associated with lower risk of COVID-19

17th September 2021

Poor metabolic health leads to worse outcomes in COVID-19 but a higher diet quality appears to reduce the risk and severity of infection.

The presence of poor metabolic health in conditions such as obesity and type 2 diabetes is known to be associated with worse outcomes in COVID-19. In fact, a higher body mass index has been found to be a causal risk factor for COVID-19 susceptibility and severity. Obesity is influenced by dietary intake but an important factor is the quality of an individual’s diet so that a higher diet quality is associated with a lower risk of obesity. Various measures have been developed to evaluate diet quality and how this can impact on the risk of chronic diseases. One such diet score is the healthful Plant-Based Diet Index (HPBDI) and which has been associated with a lower risk of developing type 2 diabetes. However, the association between diet quality and both the risk and severity of COVID-19 is less clear.

In light of this evidence gap, a team led by researchers from Harvard Medical School, Boston, US, decided to explore the relationship between diet quality and COVID-19. The team used data obtained from a smartphone app used for the COVID-19 Symptom Study to prospectively investigate the association. As well as diet, the team sought to examine how the risk of COVID-19 depends on not only on diet quality but also socioeconomic deprivation. Demographic and clinical data were collected via the smartphone app between March and December 2020, together with self-reported COVID-19 testing and symptoms. Diet quality was obtained using a short-form food frequency questionnaire and participants were asked to report how often on average, they consumed one portion of particular foods in a typical week. Using this information, the team calculated a HPDI score which ranged from 14 (lowest) to 70 (highest) with higher scores reflecting a healthier plant-based diet. Individuals were then categorised as having a low, medium or high HPDI score. The primary outcome was COVID-19 risk based on a predictive, symptom-based algorithm and multivariable Cox models were used to calculate hazard ratios (HR) for COVID-19 risk and severity.

Self-reported diet quality was available for 592,571 app users with a mean age of 56 years (68.2% female), of whom, the vast majority (96%) were of White ethnicity and the mean HPDI score for the whole sample was 50. In fully adjusted models, for individuals with the highest HPDI score compared to the lowest score, the risk of COVID-19 was reduced by 9% (HR = 0.91, 95% CI 0.88 – 0.94, p < 0.001). Furthermore, the risk of severe COVID-19 was also significantly reduced for those with the highest HPDI compared to the lowest HPDI scores (HR = 0.59, 95% CI 0.47 – 0.75, p < 0.001).

When considering socioeconomic deprivation, there was clearly an association between an increased risk of COVID-19 and diet quality. For example, among those living in an area of low deprivation and with a low HPDBI score, the risk of COVID-19 was slightly elevated (HR = 1.08, 95% CI 1.03 – 1.14). However, among those with a low HPBDI scores and living in an area of high deprivation, the risk was much higher (HR = 1.47, 95% CI 1.38 – 1.52). In fact, even among those with a high HPBDI but living in a highly deprived area, the risk of COVID-19 was still elevated (HR = 1.28, 95% CI 1.18 – 1.37, p < 0.001).
The authors concluded that a higher diet quality was associated with a reduced risk of both COVID-19 and severe disease but also that the combination of poor diet and increased socioeconomic deprivation further increased COVID-19 risk.

Merino J et al. Diet quality and risk and severity of COVID-19: a prospective cohort study. Gut 2021

Less than 1% of COVID-19 related deaths among fully vaccinated

14th September 2021

An analysis of all COVID-19-related deaths in England between the 2nd of January and July 2021, has been published by the Office for National Statistics (ONS). The data include a breakdown of all recorded deaths analysed by vaccination status. Clearly, a certain number of both infections and deaths among those who have been vaccinated, referred to as breakthrough infections, are likely to occur simply because the COVID-19 vaccines have been administered to many millions of people and none can be considered as 100 per cent effective.

The risk of becoming infected with COVID-19 is, according to the ONS infection survey, highest within the first 21 days after receipt of the primer vaccine dose. The bulletin from the ONS examines deaths in relation to vaccination status and uses age-standardised mortality rates, which adjusts for differences in the population age distribution.


There were a total of 640 deaths in those who had received two COVID-19 vaccines; 182 within 21 days of their second vaccine dose and 458, 21 days after their second dose. Together, both groups represent 1.2% of all COVID-19 related deaths although only 0.8% (458/51,281) of all deaths occurred 21 days after the second vaccine dose. In other words, less than 1% of all COVID-19 related deaths occurred in those who were fully vaccinated. However, it is worth noting that the more infectious delta variant only became the dominant strain, according to the ONS, since the end of May 2021 and hopefully future bulletins will report upon any associated mortality changes.

In cases where the date of infection was known, among those who had received two vaccinations, 47.5% became infected 14 or more days after the second dose, leading to 256 deaths.

Characteristics of individuals with breakthrough deaths

Among the 256 deaths occurring 14 or more days after infection, linked data, which provides demographic and clinical information was available for 252 individuals. The information showed that the average age of death among these fully vaccinated individuals was 84 years. Nearly two-thirds (61.1%) were male and 76.6% were described as clinically vulnerable and 13.1% of deaths occurred among immunocompromised patients.

The latest set of ONS data clearly shows that COVID-19 related deaths are significantly reduced due to vaccination but also serves as a reminder that deaths will still occur, especially among the clinically vulnerable and immunocompromised, highlighting the need for booster doses.


ONS Deaths involving COVID-19 by vaccination status, England: deaths occurring between 2 January and 2 July 2021

Risk of long COVID halved after full vaccination

3rd September 2021

Data from the COVID symptom study shows that full vaccination leads to a reduced risk of continued symptoms (i.e., long COVID).

Full vaccination against COVID-19 has led to reductions in the proportion of patients experiencing severe disease requiring hospitalisation although despite full vaccination, breakthrough infections are known to occur. It is necessary therefore to both identify and protect individuals who might be at a greater risk of re-infection after full vaccination. However, little is known about the potential risk factors for re-infection and whether or not full vaccination might reduce the incidence of persistent symptoms or long COVID.

Using data collected from the COVID Symptom Study, which is a prospective, community-based study based on self-reported data, researchers analysed the results from two patient cohorts. The first group were those who tested positive for COVID-19 at least 14 days after their first vaccination, but before their second (case group 1) and those who tested positive at least 7 days after their second vaccination dose (case group 2). The team included two match-controlled control groups, which were those with a negative COVID-19 test result during the same time-frame for the case 1 and 2 cohorts. In order to analyse the disease profiles associated with an increased risk of re-infection, the researchers selected sub-cohorts from cases 1 and 2, who continued using the app for 14 consecutive days after testing positive and again matched these to individuals who also used the app for the same period after infection but who were unvaccinated with a positive COVID-19 test result. In the analysis of risk factors and post-vaccination infection, adjustments were made for age, body mass index and sex.

There were 1,240,009 users who reported a first vaccine dose and of whom, 6030 (0.5%) subsequently tested positive for COVID-19 (case group 1). This compared with 971,504 who had received full vaccination and of whom, 2370 (0.2%) tested positive (case 2). Both groups were equally matched, with a mean age of 50.2 years and were predominately female (62.5%).

In the risk factor analysis, frailty was significantly associated with post-vaccination infection in older adults (odds ratio, OR = 1.93, 95% CI 1.50 – 2.48, p < 0.0001) and among individuals from highly deprived areas, (OR = 1.11, 95% CI 1.01 – 1.23, p = 0.039). Additionally, in older adults who received only a single vaccination, kidney disease (OR = 1.95), heart disease (OR = 1.30) and lung disease (OR = 1.27) were all significantly associated with post-vaccination infection. Interestingly, there was a significant reduction in of the risk of symptoms persisting beyond 28 days (i.e., long COVID) among those who were fully vaccinated (OR = 0.51, 95% CI 0.32 – 0.82, p = 0.006).
Commenting on their findings, the authors suggested that the data appeared to indicate that among those who were fully vaccinated, the risk of continued symptoms or long COVID appeared to be reduced by half. They concluded however, that these findings potentially support a cautious relaxation of mitigation strategies such as social distancing given the factors associated with an increased risk of re-infection.

Antonelli M et al. Risk factors and disease profile of post-vaccination SARS-CoV-2 infection in UK users of the COVID Symptom Study app: a prospective, community-based, nested, case-control study. Lancet Infect Dis 2021

Higher risk of hospitalisation from delta COVID-19 variant

A study has suggested that among unvaccinated individuals, infection with the delta COVID-19 variant doubles the risk of hospitalisation.

The emergence of COVID-19 variants, in particular the delta COVID-19 variant, is a cause for concern, especially, given evidence of reduced effectiveness of vaccines against the variant. Nevertheless, despite this, other data has indicated that vaccination protects against hospitalisation in those infected with the delta variant.

In an attempt to better characterise the severity of infection caused by the delta COVID-19 variant, a team from Public Health England, examined the relative risk of both hospital emergency care attendance or admission following infection with the variant and the extent to which this was modified by vaccination. The team used individual-level data on those with laboratory-confirmed COVID-19 infection between March 29 and May 23, 2021 and with whole viral genomic sequencing of either the alpha or delta COVID-19 variants. The risk of hospital admission and attendance at emergency care were compared for patients with either variant and by vaccination status, over a maximum of 14 days from their positive COVID-19 test. The primary analysis was the risk of hospitalisation outcomes (i.e., either admission or attendance), based on hazard ratios (HR). The main secondary analysis was the HRs for the same hospital outcomes based on vaccination status, which was dichotomised as either unvaccinated or less than 21 days since the first vaccine dose or 21 or more days since the first dose. Results were adjusted for age, sex, area of residence (based on deprivation) and the presence of any international travel within 14 days of a positive test.

Over the period of the study, there were 43,338 cases included in the analysis with 8,682 infections with the delta COVID-19 variant and 34,656 with the alpha variant. In addition, the majority of patients in both groups (74%) were unvaccinated. The median age of those infected with the delta COVID-19 variant was 29 years (48.9% female) which was slightly lower than those with the alpha variant (median age 31 years, 51.7% female). The estimated risk for hospitalisation within 14 days was higher with the delta COVID-19 variant compared with the alpha variant (adjusted HR, aHR = 2.26, 95% CI 1.32 – 3.89). Similarly, there was an increased risk for hospital admission or emergency care attendance within 14 days of infection for the delta compared with the alpha variant (aHR = 1.45, 95% CI 1.08 – 1.95).

When the data were analysed in terms of vaccination status, among those who were either unvaccinated or who had been vaccinated less than 21 days before infection, the risk of hospital admission was also higher among individuals with the delta COVID-19 variant (aHR = 2.32, 95% CI 1.29 – 4.16) and in those 21 days after their first vaccine dose although there was less precision over this outcome due to the wide confidence intervals (aHR = 1.94, 95% CI 0.47 – 8.05). This increased risk was also evident for the combination of hospital admission or emergency care attendance (aHR = 1.58, 95% CI 0.69 – 3.61).
In discussing their findings, the authors recognised that their estimates of the impact of vaccination was imprecise and that further work was needed to confirm the impact of vaccination on breakthrough infections. They concluded that among unvaccinated individuals, infection with the delta COVID-19 variant, doubles the risk of hospital admission.

Twohig KA et al. Hospital admission and emergency care attendance risk for SARS-CoV-2 delta (B.1.617.2) compared with alpha (B.1.1.7) variants of concern: a cohort study. Lancet Infect Dis 2021.

Risk of clotting disorders higher after COVID-19 than vaccination

27th August 2021

A study suggests that the risk of clotting disorders appears to be significantly higher with COVID-19 infection compared to vaccination.

Published studies reporting the appearance of the clotting disorders thrombocytopenia and thrombosis after vaccination with the COVID-19 vaccine, ChAdOx1 in several European countries is a cause for concern. Nevertheless, while it appears that these adverse effects are rare, some countries have limited the use of this particular vaccine. Trying to establish whether clotting disorders are caused entirely by exposure to a COVID-19 vaccine is hampered by the fact that such clotting disorders have also been observed as a result of infection with the virus. In trying to untangle this association and to provide some much-needed perspective, a group of researchers led by the Nuffield Department of Primary Health Care Sciences, University of Oxford, UK, have examined the link between COVID-19 vaccination and the risk of thrombocytopenia and thromboembolic events in England. The researchers used a self-control case series analysis (i.e., where the individual acts as their own control) with patients between December 2020 to April 2021. They assessed the risk of these adverse clotting disorders among those who were vaccinated with the two COVID-19 vaccines, ChAdOx1 and BNT162b and the incidence of thrombotic events among the same individuals who tested positive for COVID-19. Included participants were aged 16 years and over who had received their first dose of either ChAdOx1 or BNT162b. They used three composite primary outcomes; hospital admission or death associated with one of the clotting disorders, i.e., thrombocytopenia, venous thromboembolism and arterial thromboembolism.

There were 19,608,008 people who received the ChAdOx1 vaccine, 9,513,625 the BNT162b and a total of 1,758,095 who had a positive COVID-19 test. In addition, during the study period, 9,764 people were hospitalised because of thrombocytopenia and 52 of these individuals died. An increased risk of thrombocytopenia was observed 8 – 14 days after the ChAdOx1 vaccine (incidence rate ratio, IRR = 1.33, 95% CI 1.19 – 1.47) and also after 22 – 28 days (IIR = 1.26). However, the risk associated with a positive COVID-19 test after 8 – 14 days was much higher (IIR = 5.27, 95% CI 4.34 – 6.40) and after 22 – 28 days (IIR = 1.50). For venous thromboembolism after the ChAdOx1 vaccine at days 8 – 14, the IIR was 1.10 but again much higher after a positive COVID-19 test during the same time period (IIR – 13.86). For BNT162b, the risk of thrombocytopenia was also increased between days 8 – 14 but not significant (IIR = 1.02, 95% CI 0.89 – 1.17).
Using these results, the authors estimated the excess number of adverse clotting disorders per 10 million exposed to each vaccine compared to a positive COVID-19 test. With the ChAdOx1 vaccine, this amounted to 107 excess thrombocytopenia events and 66 excess thromboembolism events. In contrast, for a positive COVID-19 test result, the corresponding values were 934 excess thrombocytopenia events and 12,614 excess thromboembolism events.
The authors concluded that while adverse clotting events did occur after COCVID-19 vaccination, these events were significantly less than those associated with being infected with the virus.

Hippisley-Cox J et al. Risk of thrombocytopenia and thromboembolism after covid-19 vaccination and SARS-CoV-2 positive testing: self-controlled case series study. BMJ 2021

Major barriers to COVID-19 mitigation strategies in African countries

Barriers to implementing COVID-19 mitigation strategies in African countries include overcrowding and lack of washing or toilet facilities.

According to the World Health Organisation (WHO), the spread of COVID-19 is predominately through airborne respiratory droplets. While the available COVID-19 vaccines are effective against the virus, a report by WHO in April 2021, found that less than 2% of the world’s COVID-19 vaccines were administered in Africa. As a result and until vaccine supplies increase, individuals within these countries, should continue with mitigation strategies such as social distancing, the wearing of face-masks and hand-washing. In fact, there is evidence that such mitigation strategies will slow the spread of COVID-19. However, data suggests that COVID-19-related deaths are rising in many African countries indicating a possible failure to implement mitigation strategies.

In trying to examine how living conditions in African countries might impact on the ability of households to undertake mitigation strategies, a team from the Department of Medicine, Geffen School of Medicine and Department of Epidemiology, University of California, US, turned to household survey data collected from 54 African countries. These surveys had examined several different factors such as the number of people per household team, access to water, use of soap, toilet facilities etc. The researcher were particularly interested in assessing how these factors might impact on household’s capacity to practise mitigation strategies. They examined the ability to participate in social distancing for example, based on the reported number of household individuals, the capacity for hand-washing, based on whether the house had access to piped, well or spring water within the dwelling, access to toilet facilities and the risk of intergenerational transmission based on the number of individuals aged 60 years and older living in households with younger people.

Household data was available for 54 African countries and the surveys had been conducted between the years 2000 and 2020, providing information on 3,471627 individuals. In 36 of the 54 countries, the median number of households with 6 or more people was 56% (95% CI 51% – 60%) and this figure ranged from 14% in Mauritius to 86.1% in Senegal. Moreover, the median number of households in which 3 or more people shared a single sleeping room was 15% (95% CI 13% – 19%). Of most concern was how a median of 71% of households lacked access to water within the household or on their plot of land. A total of 43 countries provided data on use of soap in the home, of which a median of 56% reported no use of soap or household washing facilities. Furthermore, a median of 45% of households had no toilet at home. Finally, the proportion of people living in multigenerational households ranged from 8.5% to 55.8%.
Discussing these findings, the authors stated that given the extent of household overcrowding, apparent lack of soap use at home, washing facilities and access to in-house toilets, would make it extremely difficult for millions of Africans to implement COVID-19 mitigation strategies. They concluded that such data highlighted the urgency of ensuring that vaccines reach Africans to both prevent disease and contain the pandemic.

Brewer TF et al. Housing, sanitation and living conditions affecting SARS-CoV-2 prevention interventions in 54 African countries. Epidemiol Infect 2021

Transmission of COVID-19 more likely from very young children

24th August 2021

In a study where the index case was less than 18 years, children aged 0 – 3 years were mainly responsible for the transmission of COVID-19.

Over the course of the pandemic, the role of children in the transmission of COVID-19 has been investigated and there is a general sense that children do not play and important role. This perception was re-iterated in a review from May 2020 of over 47 articles which also concluded that children are unlikely to be the main drivers of the pandemic. Nevertheless, one important source of infection is through household transmission, with one analysis of 54 studies and over 77,000 participants, indicating a household transmission rate of 16.6%. But to what extent are young people responsible for household transmission? Some studies examining the transmission of COVID-19, have suggested that it was more likely from those aged 20 years or less. In contrast, a recent systematic review concluded that there is a reduced transmission potential both from and to, individuals younger than 20 years of age.

In trying to more closely examine the relationship between age and household transmission, a team from the Health Protection, Public Health Ontario, Canada, undertook an age analysis where the index case of COVID-19 was a paediatric household member between June and December 2020. They divided paediatric index cases into four age grouping; 0 – 3, 4 – 8, 9 – 13 and 14 – 17 years. Since other factors might have been responsible for the transmission, the team also sought information on school/child-care factors. The main outcome of interest was secondary household transmission of COVID-19 infection by a paediatric index case between one and fourteen days after the paediatric index case. In determining cases, the team compared symptom onset dates of cases within the household. Regression analysis was used to identify the odds of household transmission, adjusting for gender, month of disease onset and mean family size.

There was a total of 6,280 private households with a paediatric index case for which the mean age was 10.7 years (45.6% female). From this total, 27.3% experienced a secondary household transmission of COVID-19. In the fully adjusted model, the odds of transmission of COVID-19 for children aged 0 – 3 years was significantly higher than those aged 14 – 17 years (odds ratio, OR = 1.43 (95% CI 1.17 – 1.75). This association was found irrespective of factors such as the presence of symptoms, or with any school/child-care outbreaks. It was also found that children aged 4 – 8 years had a significantly higher odds for transmission (OR = 1.40) compared to those aged 14 to 17 years although this was absent among children aged 9 – 13 (OR = 1.13, 95% CI 0.97 – 1.32).
In their discussion, the authors noted that as the number of paediatric cases increases worldwide, children were likely to play an important role as vectors for the transmission of COVID-19. Moreover, their data indicated that it was the younger rather than older children who would be the source of infection.

Paul LA et al. Association of Age and Pediatric Household Transmission of SARS-CoV-2 Infection. JAMA Pediatr 2021

No benefit from early convalescent plasma in high-risk COVID-19 patients

23rd August 2021

Convalescent plasma has no effect on COVID-19 disease progression when given later in the course of illness but could help if given earlier.

The use of convalescent plasma (CP) in patients with COVID-19 is based on the notion that the administered plasma, by containing therapeutic antibodies to the virus, enables recovery. However, to date, results with this therapy have been disappointing, prompting the RECOVERY trial in the UK to halt recruitment to the CP arm in January 2021. In fact, studies have shown how the use of CP in those with severe COVID-19 infection, did not result in any improvements compared to standard care. Nevertheless, in these studies, CP was administered to patients late in their disease. Furthermore, and there is some evidence from a small study in 80 older patients that when CP was given within 72 hours of the onset of mild COVID-19, it did result in reduced illness progression.

In an attempt to provide more robust evidence for the benefit of early use of CP in those with COVID-19, a team from Michigan State University, US, decided to undertake a randomised, multi-centre, single-blind trial in patients who presented at an emergency department within seven days of developing COVID-19 symptoms. The researchers wanted to examine if the early administration of CP was able to halt disease progression. All participants had PCR confirmed COVID-19 infection and were aged 50 years or older and with one or more known risk factors for disease progression. Individuals were randomised in a 1:1 fashion to either one unit of convalescent plasma or saline (placebo) which was coloured to resemble the plasma. The primary outcome of the study was disease progression within 15 days of randomisation and which was defined by a composite of hospital admission, seeking emergency/urgent care or death without hospitalisation.

A total of 511 patients underwent randomisation, 257 to plasma with a mean age of 54 years (52.5% female). Risk factors included a body mass index greater than 30 (59.1%), hypertension (40.9%) and diabetes (29.6%). In fact, overall, 54.9% of those assigned to convalescent plasma had three or more COVID-19 risk factors. The primary outcome occurred in 30% of those given CP and 31.9% of those given saline. Furthermore, subgroup analysis, i.e., by body mass index, age, ethnicity etc, also showed no important differences. Within 30 days of administration of either treatment, death occurred in 1.9% of those given plasma and 0.4% given saline.
In their discussion, the authors noted that there was a potentially sound rational for giving early convalescent plasma, i.e., that it would boost the level of neutralising antibodies before an individual could develop their own sufficient antibody response. Despite this obvious possible benefit, the authors concluded that even that even among those with a number of risk factors for COVID-19 disease progression, early use of convalescent plasma had no impact on clinical outcomes.


Korley FK et al. Early Convalescent Plasma for High-Risk Outpatients with Covid-19. New Eng J Med 2021

Over 1 in 10 COVID-19 infections were hospital-acquired

16th August 2021

An analysis of COVID-19 infections during the first wave has revealed that just over 1 in 10 of these infections were hospital-acquired.

During the first wave of the COVID-19 pandemic there were a huge number of patients admitted to hospital. Ensuring minimal hospital-acquired infection was therefore of paramount importance, especially as earlier research with SARS and MERS had shown that human-to-human transmission occurred mainly within the healthcare setting. In a letter to the Lancet, a team from Lancaster Medical School, Lancaster University, UK, have examined the extent to which nosocomial, i.e., hospital-acquired, COVID-19 infections occurred during the first wave of the pandemic. The researchers used records contained in the International Severe Acute Respiratory Emerging Infection Consortium (ISARIC) and which has already reported on the clinical characteristics of 20,133 hospital in-patients during the initial phase of the pandemic. For the current analysis, the team examined records of patients enrolled in the UK arm of ISARIC and who had an onset of symptoms before the beginning of August 2020. In trying to determine whether patients were likely to have a hospital-acquired infection, the team considered both their admission date and the date of symptom onset. They used the recorded infection date for a patient and identified those who were admitted before infection, as likely candidates for a hospital-acquired infection.

The researchers estimated that there were 82,624 patients admitted to hospital before the beginning of August 2020 and found that 11.3% (95% CI 11.1 – 11.6) of these became infected with COVID-19 after admission to hospital. When restricting their analysis to the middle of May 2020, this proportion increased to 15.8% (95% CI 15.8 – 19.6). Using a more conservative estimate of symptom onset at least 14 days after hospital admission, the proportion reduced to 6.8%. An interesting additional finding was how there was marked heterogeneity between hospital trusts. For example, in cases where the trust provided both acute and general care, the incidence of infections was 9.7% (95% CI 9.4 – 9.9) whereas this was substantially higher in residential community care hospitals (61.9%, 95% CI 56.4 – 68) and in mental health hospitals (67.5%). The authors were unable to account for this extreme variation and called for an urgent investigation to identify and promote best practice for infection control.
In discussing these findings, they identified that a recognised limitation of the ISARIC dataset was that it was unable to identify patients infected during admission or those who were discharged before developing symptoms and who might have acquired their infection within the hospital. In other words, the authors felt that their overall estimate of the nosocomial infection rate is probably an underestimate. The concluded that with lessons learnt from the first wave coupled with the development of vaccines, NHS infection control policies should now be sufficiently robust to prevent the burden of hospital-acquired infections.

Read JM et al. Hospital-acquired SARS-CoV-2 infection in the UK’s first COVID-19 pandemic wave. Lancet 2021

Increased rate pre-term births in mothers with COVID-19

A comprehensive analysis has found an increase rate of pre-term births in those with COVID-19 but was otherwise reassuring.

Pregnant women have been deemed to be at a higher risk of severe illness from COVID-19. Moreover, in a systematic review in May 2020, it was concluded that mothers infected with COVID-19 were at an increased risk of pre-term birth although the authors urged caution, as their data were derived from a small number of cases and also included the SARS and MERS viruses. In order to provide as much information as possible on the pregnancy outcomes associated with COVID-19 infection, a team from the Department of Obstetrics and Gynaecology, St George’s University Hospitals NHS Foundation Trust, London, UK, undertook a systematic review of all available literature on COVID-19 and pregnancy in order to provide comprehensive data and to direct the course of ongoing research and studies. They searched all major databases and included a wide range of studies e.g., case reports, case series, and randomised trials, provided that studies reported on women with a PCR-confirmed diagnosis of COVID-19. Extracted information on maternal outcomes including clinical symptoms, laboratory findings, any obstetric complications and perinatal outcomes including death and vertical transmission were also collected.

A total of 86 studies were identified which included 2567 pregnancies. Nearly a third of mothers (30.6%) were older than 35 years and half of the cohort (50.8%) were of Black, Asian or other ethnic minority groups. Overall, antiviral therapy was given to a fifth (21.1%) of women though a much higher proportion (51.15%) received anticoagulation and 18.2% required nasal or non-invasive oxygen support.
COVID-19 symptoms were predominately cough (71.4%), fever (63.3%), dyspnoea (34.4%) and loss of taste or smell (22.9%). The most common laboratory abnormality was a raised D-dimer (84.6%), followed by a raised C-reactive protein or procalcitonin (54%). Fortunately, only 7% of women needed admission to an intensive care unit. Pre-term birth which was primarily iatrogenic was found to be common (21.8%) though this was medically indicated in 18.4% of all cases. The incidence of neonatal COVID-19 infection was low at 1.2%.

Commenting on their findings, the authors noted that generally, pregnancy outcomes were good. The incidence of admission to maternal intensive care was low and likely to be similar to the rates for other non-infected women. Furthermore, there was a very low incidence of maternal mortality. The authors did note how their analysis had several limitations including the retrospective nature of most studies and a lack of standardisation of care, given that studies came from several different countries. While the incidence of vertical transmission appeared to be low, the authors felt that more evidence was needed to confirm whether this represents a significant problem. However, there was a higher-than-average increase in pre-term births which was consistent with findings from other studies.

Khalil A et al. SARS-CoV-2 infection in pregnancy: A systematic review and meta- analysis of clinical features and pregnancy outcomes. EClinicalMedicine 2021