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mRNA-1273 vaccine associated with lower risk of COVID-19 outcomes than BNT162b

Rod Tucker
8 December, 2021  

mRNA-1273 appears to be associated with a lower risk of COVID-19-related outcomes such as infection, hospitalisation and death compared to BNT162b. This was the finding of the first head-to-head vaccine effectiveness analysis undertaken by a group of researchers from the Brigham and Women’s Hospital, Harvard Medical School, Boston, US.

Randomised controlled trials have already demonstrated the effectiveness of the currently available COVID-19 vaccines. For instance, the mRNA-1273 vaccine (Moderna) has an efficacy of 94.1% at preventing COVID-19 illness and that a similar efficacy (95%) has been observed for BNT162b (Pfizer-BioNTech).

However, despite this near identical level of efficacy, other work has suggested that there might be differences between these two vaccines, even though they have the same mode of action. One study, for example, indicated that the mRNA-1273 vaccine produced a higher humoral immunogenicity than BNT162b, while other data show that the Moderna vaccine it is associated with a two-fold reduced risk of breakthrough infections compared to BNT162b and also results in a lower incidence of COVID-19-related hospitalisations.

For the present study, the US team turned to data from the national healthcare databases of the Department of Veterans Affairs, which is the largest US integrated healthcare system. The researchers sought to compare the relative effectiveness of the Moderna and Pfizer-BioNTech vaccines with respect to documented COVID-19 infections, symptomatic COVID-19, hospitalisation, admission to an intensive care unit (ICU) and death. In addition, the team examined the effectiveness of the two vaccines against the delta COVID-19 variant and examined these outcomes after 24 weeks.


During the period of study, there were 367,113 recipients of the BN162b and 397,690 of the mRNA-1273 vaccines. Over a 24-week period, 2016 COVID-19 infections were documented, of which 559 were detected as symptomatic, 411 which led to hospitalisation, 125 ICU admissions and 81 deaths.

The absolute risk of infection was low in both vaccine groups; 5.75 events per 1000 persons with the Pfizer-BioNTech and 4.52 with the Moderna vaccine. The 24 week risk ratio for infections for BNT162b compared to mRAN-1273 was 1.27 (95% CI 1.15 – 1.42), 1.39 for symptomatic infection, 1.70 for hospitalisation, 1.38 for ICU admission and 1.11 for death. Each of these risks was statistically significant apart from the risk of death. The overall risk difference expressed as events over 24 weeks per 1,000 persons was 1.23 for a documented infection.

Using these data, the authors calculated the number needed to vaccinate with mRNA-1273 instead of BN162b to prevent one case of documented infection was 813.

Analysis during the time period characterised by dominance of the delta COVID-19 variant, there was a 58% higher risk of infection in those vaccinated with BNT162b although this difference was non-significant (risk ratio = 1.58, 95% CI 0.85 – 2.33).

Commenting on these findings, the authors highlighted how their study had shown that recipients of the BNT162b vaccine had a 27% higher risk of a documented COVID-19 infection and a 70% increased risk of hospitalisation compared to the Moderna vaccine.

They concluded that the data provided evidence of a lower 24-week risk of COVID-19-related outcomes among those receiving the m-RNA-1273 vaccine compared to BNT162b.


Dickerman BA et al. Comparative Effectiveness of BNT162b2 and mRNA-1273 Vaccines in U.S. Veterans. New Eng J Med 2021