Efficacy
Among 36,523 subjects without evidence of existing or prior COVID-19 infection, 8 cases of COVID-19 with onset at least 7 days after the second dose were seen among vaccine recipients and 162 among placebo recipients, corresponding to 95.0% vaccine efficacy (95% credible interval, 90.3%-97.6%).
“Supplemental analyses indicated that vaccine efficacy among subgroups defined by age, sex, race, ethnicity, obesity, and presence of a coexisting condition was generally consistent with that observed in the overall population,” the authors wrote.
Between the first and second doses, 39 cases of COVID-19 were observed among BNT162b2 recipients and 82 cases among placebo recipients, corresponding to 52% vaccine efficacy during the 21-day interval (95% CI, 29.5%-68.4%) suggesting early protection may begin as soon as 12 days after the first injection.
“This is an incredible achievement given that an effective vaccine has never been developed and approved for use in such a short timeframe,” Dr. Bowton explained. “That the vaccine is highly effective in reducing the incidence of symptomatic COVID-19 seems incontrovertible.”
Dr. Douglas S. Paauw
“This vaccine has shockingly amazing efficacy and is well tolerated, and the results are beyond even optimistic projections,” Douglas S. Paauw, MD, of the University of Washington, Seattle, said in an interview.
Questions remain
“It is not yet known if the vaccine prevents asymptomatic infections, with their attendant risk of contagion, as rates of seroconversion of trial participants against betacoronavirus nucleoproteins not included in the vaccine has not been reported,” Dr. Bowton commented.
“Common questions our patients will ask us remain unanswered for now, [including] how long will the protection last, is it safe in pregnant women, and does it prevent asymptomatic infection,” Dr. Paauw explained. “We do not know everything about longer term side effects, but the benefits of this vaccine appear to outweigh the risks of the vaccine.”
The researchers noted these and other limitations in their report, acknowledging that longer follow-up is needed to evaluate long-term safety of the vaccine.
This study was supported by BioNTech and Pfizer. Several authors disclosed financial relationships with Pfizer and other pharmaceutical companies outside the submitted work. Dr. Bowton and Dr. Paauw had no conflicts to disclose.
SOURCE: Polack FP et al. N Engl J Med. 2020 Dec 10. doi: 10.1056/NEJMoa2034577