Preprint shows strong but fading efficacy of Pfizer vaccine at six months

An ongoing study involving the BNT162b2 COVID-19 vaccine from Pfizer (NYSE:PFE) and BioNTech (NSDQ:BNTX) could potentially underscore the need for boosters. But more data are needed to understand vaccine performance over time, according to a preprint published on MedRxiv.

Pfizer CEO Dr. Albert Bourla has previously predicted that booster doses of the vaccine would be needed. Still, the U.S. government has yet to embrace that view for the general population. A CDC advisory committee, however, recently endorsed the use of boosters in immunocompromised patients.

The study found that the efficacy of the BNT162b2 vaccine peaked between seven days to less than two months after the administration of the second dose. Four-to-six months after the second dose administration, the efficacy waned to 83.7%. Efficacy declined an average of roughly 6% every two months, according to the paper. “Ongoing follow-up is needed to understand persistence of the vaccine effect over time, the need for booster dosing, and timing of such a dose,” the report authors concluded.

Across the six-month trial period, the vaccine was 97% effective at preventing severe disease.

Most patients tolerated the vaccine well, but the study reported several adverse events associated with the vaccine not identified in prior studies. These include decreased appetite, lethargy, asthenia (physical weakness), malaise, night sweats and hyperhidrosis (abnormal sweating).

The study involved 44,000 participants.

Absent from the study was an analysis of how the fast-spreading variant impacts vaccine efficacy.

The company, however, separately released data in its earnings conference indicating that the third dose of its vaccine led to a five-fold increase in antibody titers over dose-two levels in people 18 to 55 years old. For those 65 to 85, a third dose increased antibody titers 11 fold.

Pfizer and its partner BioNTech are also developing a Delta-variant vaccine. It expects clinical trials for that vaccine to begin next month.