Myocarditis rate higher in younger people following mRNA vaccination

5th December 2022

Although the myocarditis rate after mRNA vaccination is low these rates appear to higher in those aged 18 – 30 compared to older adults

The overall myocarditis rate following a mRNA vaccination for COVID-19 is generally low but is higher than expected among those aged 12 to 29 years of age according to the findings of a post-marketing observational study by Canadian researchers.

Although there has been a huge uptake of COVID-19 vaccines, hesitancy remains a significant challenge with acceptance rates ranging from 53.6 to 84.4%. In fact, a US survey of 5,088,772 individuals identified that almost half (49.2%) of vaccine hesitant respondents reported fear of side effects. One such adverse effect following vaccination and which was not identified during the clinical trials was myocarditis with one US surveillance study concluding that the risk of myocarditis after receiving mRNA-based COVID-19 vaccines was increased across multiple age and sex strata and highest after the second vaccination dose in adolescent males and young men. However, little is known about the incidence of the condition following a third vaccination dose and this was the subject of the current study in which the Canadian team compared the myocarditis rate after a first, second and third dose compared to the background or expected rate.

The team used an integrated COVID-19 surveillance platform which contained all COVID-19-related data including infections and hospital or intensive care admissions. They focused on individuals aged 12 years and older and set the primary outcome as hospital admission or an emergency department visit for myocarditis.

Myocarditis rate and mRNA vaccination

During the study period (December 2020 to March 2022), a total of 1,025,385 doses of an mRNA vaccine (mRNA-1273 and BNT162b) were administered.

A total of 99 incident cases of myocarditis were identified within 7 days of vaccination, giving a rate per 100,000 of 0.97 (95% CI 0.78 – 1.17). The expected rate was 0.13 (95% CI 0.06 – 0.28) so that the observed:expected (OE) ratio was 14.81. The observed rate was higher in males than females (1.64 vs 0.35) and occurred in younger men (median age males = 28 vs median age females = 45).

Within 21 days following vaccination, there were 141 cases of myocarditis with an OE ratio of 7.03 (95% CI 5.92 – 8.29). As with the 7-day risk period, the 21-day incidence rate was higher in men than women (2.15 vs 0.67). In fact, when researchers looked at the incidence rate across different ages, the rates were much higher among those aged 12 – 29. For example, the incidence rate was 2.95 (ages 12 – 17) and 2.97 (ages 18 – 29) compared to 0.77 (ages 50 – 59) and 0.71 (ages 60 – 69).

Interestingly, the incidence myocarditis in both the 7 and 21-day post-vaccination periods reduced after the second dose. For example, the incidence rate during the first 7 days after the first vaccination was 0.18, 1.90 after the second dose but 0.76 after the third dose.

When comparing vaccines, there was a much higher rate of myocarditis following mRNA-1273 compared to BNT162b (1.44 vs 0.74). In addition, the incidence rate was highest among males aged 18 – 29 after the second dose (22.97 vs 5.84, mRNA vs BNT162b).

The authors concluded that although absolute rates of myocarditis were low, their findings support the preferential use of the BNT162b2 vaccine over the mRNA-1273 vaccine for people aged 18-29 years.

Citation
Naveed Z et al. Observed versus expected rates of myocarditis after SARS-CoV-2 vaccination: a population-based cohort study. CMAJ 2022

mRNA-1273 vaccine response non-inferior to young adults in children from 6 months

10th November 2022

The mRNA-1273 vaccine has been shown to generate an antibody response in children from 6 months that is non-inferior to young adults

The mRNA-1273 vaccine directed against COVID-19 has been shown to produce an antibody response in children aged from 6 months to 5 years that was comparable to the response elicited by young adults, aged 18 to 25 according to the findings of a study by US researchers.

It has become recognised that the efficient transmission of COVID-19 from school-age children and adolescents to household members can occur and lead to the hospitalisation of adults with secondary cases of the virus. While both COVID-19 infections and deaths are less frequent in children compared to adults it has been estimated that of 4.1 million COVID-19 deaths, 0.4% (16,100) occurred in those under 20 years of age and of which, 47% were in those age 0 to 9 years. Vaccination against COVID-19 is known to be effective at reducing hospitalisation and death in adults and the mRNA-1273 vaccine is also known to be safe and effective at inducing an immune response and preventing COVID-19 in children 6 to 11 years of age. However, whether the vaccine remains safe and able to elicit a satisfactory antibody response in children from 6 months of age is uncertain and was the purpose of the present study.

The US researchers undertook a phase 2 – 3 trial to determine the most appropriate dose in younger children. This revealed that a 25-μg dose of the mRNA-1273 vaccine was safe in children from 6 months of age. The team then randomised children aged 6 months to 23 months and between 2 and 5 years in a 3:1 ratio to two 25-μg doses administered 28 days apart or matching placebo. The aim of the study was to assess whether the antibody response was non-inferior to that generated by those aged 18 to 25.

mRNA-1273 vaccine antibody response in children from 6 months

A total of 1761 children with a median age of 16 months (51.7% male) received two doses of the vaccine and of whom, 89.4% tested negative for COVID-19. The median duration of follow-up was 68 days.

When assessed at day 57, the neutralising antibody geometric mean concentration was 1781 (95% CI 1272 – 1563) among those aged 6 – 23 months. This compared to a mean concentration of 1391 in those aged 18 to 25 (who had received 2 x 100 μg doses) and met the pre-defined criteria for non-inferiority. A similar and non-inferior response was also generated in those aged 2 – 5 years. In addition, there were no major safety concerns with adverse events mainly low-grade and transient.

In terms of vaccine effectiveness, within the 6 – 23-month group, infection occurred in 3.4% of the mRNA-1273 vaccine group and 6.6% of the placebo group, giving a vaccine efficacy of 50.6% (95% CI 21.4 – 68.6%). Among those aged 2 to 5, the vaccine efficacy was 36.85 (95% CI 12.5 – 54%) during the period of time when Omicron was the predominately circulating variant.

The authors concluded that two 25-μg doses of the vaccine were found to be safe in children 6 months to 5 years of age and elicited immune responses that were noninferior to those in young adults.

Citation
Anderson EJ et al. Evaluation of mRNA-1273 Vaccine in Children 6 Months to 5 Years of Age. N Eng J Med 2022

Study assesses response to a third COVID vaccination in kidney transplant patients

29th July 2021

Even after a third COVID-19 vaccine dose, only half of kidney transplant patients developed a sufficient antibody response to vaccination.

Among immunocompromised individuals such as kidney transplant patients, a single COVID-19 vaccine dose has been found to elicit a sufficient response in only 17% of individuals. Furthermore, after a second dose, the response only increased to 54%. With evidence of a lower immune response to vaccination, the French National Authority for Health issued a recommendation in April 2021, that immunosuppressed, recent bone marrow transplant, those on dialysis, and patients with autoimmune diseases who did not respond after two doses of a COVID-19 vaccine, should be offered a third dose.

Given the evidence that even among kidney transplant patients who are fully vaccinated, severe COVID-19 can develop, a team from the Department of Nephrology and Transplantation, Strasbourg University Hospital, France, set out to assess the response to a third vaccination among kidney transplant patients who had an inadequate response to a second vaccination dose. The team examined the effect of the mRNA-1273 (Moderna) vaccine and included all kidney transplant patients who had no prior history of infection with COVID-19 and had anti-spike IgG antibody levels less than 50 arbitrary units, one month after administration of the second vaccination dose. They set a minimum antibody titre level of 50 units, so that any responses above this level could be considered as positive.

Findings
A total of 159 kidney transplant recipients with a median age of 57.6 years (61.6% male) and a median time from transplantation of 5.3 years were included in the analysis. After the second dose of vaccine, 59.7% (95) of patients had not generated an antibody response and the remaining patients showed a response below the positivity limit (6.8–49.9 units). The third vaccine dose was administered a median of 51 days after the second dose and the antibody response was then measured approximately 28 days after this third injection. However, at this time-point, only 49% of patients had antibody levels above 50 units. In addition, a response to the third vaccination was much more likely among those who had developed a response to the second dose (81.3% vs 27.4%, p = 0.01, second dose responders vs non-responders). The results also showed how kidney transplant patients prescribed a combination of tacrolimus, mycophenolate and steroids, were much less likely develop a response than those treated with other regimes (35% vs 63%, p = 0.006). No other factors such as sex, years since transplantation, or serum creatinine levels, had an effect on the development of an antibody response.

The authors reported on how despite three vaccination doses, 51% of kidney transplant patients failed to generate a positive antibody response and that this was more likely among those prescribed a triple therapy regime and concluded that kidney transplant patients should be offered a third vaccination dose.

Citation
Benotmane I et al. Antibody Response After a Third Dose of the mRNA-1273 SARS-CoV-2 Vaccine in Kidney Transplant Recipients with Minimal Serologic Response to 2 Doses. JAMA 2021