Efficacy and Safety of the mRNA-1273 SARS-CoV-2 Vaccine
RCT for the Moderna COVID-19 vaccine (n=30,420) found that it had a 94.1% efficacy (95% CI 89.3 to 96.8%). Moderate, transient reactogenicity occurred more frequently with the vaccine than placebo, but serious adverse events were rare, with similar incidence between arms.
Source:
New England Journal of Medicine
SPS commentary:
An editorial comments that in the study, all cases of severe COVID (30 participants) occurred in the placebo arm, and therefore protection from severe disease appears to be 100%.
It notes however that several major issues remain regarding the ability of Covid-19 vaccines to mitigate the SARS-CoV-2 pandemic. First, what are the nature and the duration of the protective immune response to SARS-CoV-2? Evidence in vaccinated monkeys suggests that SARS-CoV-2 neutralizing antibodies are the primary mode of protection, and CD8 T-cell responses can augment protection. How long neutralizing antibodies will last is not known, although follow-up studies in the phase 1 mRNA-1273 trial demonstrated persistence of neutralizing antibodies 3 months after the second dose of vaccine. Second, since reactogenicity was more common in vaccine recipients, it is possible that they were less inclined to believe that minor symptoms were due to Covid-19 and therefore less likely to refer themselves for testing in the trial. Third, analysis of virus escape from protective immune responses and long-term follow-up for rare safety events are needed. Finally, the trial was not powered to determine whether mRNA-1273 could protect against asymptomatic SARS-CoV-2 infection, a question that is critical to controlling the pandemic. Studies designed to answer this question are ongoing or planned.
It concludes that although the Covid-19 pandemic is currently raging, the prospects for control of this and future pandemics are bright. The next challenge is to get these and the next Covid-19 vaccines to the people most at risk as quickly as possible.