Pfizer and BioNTech Announce Updated Phase 3 Trial Results Showing 91.3% Efficacy and 100% Protection Against B.1.351 Variant in South Africa

“Are COVID-19 vaccines effective against newly emerging mutant strains?” “Will COVID-19 vaccines require annual booster shots, similar to flu vaccines?” As global vaccination efforts expand, questions regarding the efficacy and durability of COVID-19 vaccines persist. Today, Pfizer and BioNTech announced the latest results from the Phase 3 clinical trial of their jointly developed COVID-19 vaccine, BNT162b2. Data as of March 13, 2021, showed that BNT162b2 achieved 91.3% efficacy in preventing COVID-19, with protection lasting at least six months. Clinical trial data from South Africa (n=800), where the B.1.351 variant was prevalent, demonstrated 100% vaccine efficacy. For those hoping for long-lasting protection from COVID-19 vaccines, these findings represent welcome news.

The data previously released during the FDA review of BNT162b2 were based on an assessment of 170 symptomatic COVID-19 cases, at which time the vaccine efficacy of BNT162b2 was 95%. The data released today are based on an assessment of 927 symptomatic COVID-19 cases, including 850 cases from the placebo group and 77 cases from the BNT162b2 group, yielding a vaccine efficacy of 91.3% (95% CI: 89.0, 93.2).

The latest results also provide additional insights into the prevention of severe disease. At the time of data analysis on November 18 last year, a total of 10 cases of severe COVID-19 were identified in the clinical trial, with only one case from the vaccine group. The most recent results released today include 22 cases of severe COVID-19, still with only one case from the vaccine group. This indicates that no new cases of severe COVID-19 emerged in the vaccine group between the two analyses.

Previous studies have shown that the SARS-CoV-2 variant B.1.351, first identified in South Africa, can evade recognition by neutralizing antibodies present in the serum of some convalescent patients or vaccinated individuals, potentially reducing vaccine efficacy. The data released today included 800 volunteers enrolled in South Africa. Among these volunteers, nine symptomatic COVID-19 cases were identified, all of whom were in the placebo group, indicating a vaccine efficacy of 100% (95% CI, 53.5–100.0). Sequencing analysis of the viral strains infecting these nine patients revealed that six were infected with the B.1.351 variant.

Although the clinical trials conducted in South Africa involved a relatively small number of participants, and the protective efficacy against the B.1.351 variant remains to be further confirmed, the current trial results are consistent with those from neutralizing antibody assays targeting SARS-CoV-2 mutant strains. Experimental results published in March in the New England Journal of Medicine showed that sera from volunteers who received the BNT162b2 vaccine exhibited neutralizing activity against the B.1.351 variant, as well as against the B.1.1.7 and P.1 variants initially identified in the United Kingdom and Brazil, respectively. Although the neutralizing capacity against the B.1.351 variant was reduced compared to that against the wild-type strain, it remained at a high level. Current data do not indicate that this reduction affects the vaccine’s protective efficacy against this mutant strain.

In terms of safety, more than 12,000 volunteers who received two doses of the vaccine have been followed up for at least 6 months, with no serious safety issues identified.

Note: The original text has been abridged.

References:

[1] Pfizer and BioNTech Confirm High Efficacy and No Serious Safety Concerns Through Up to Six Months Following Second Dose in Updated Topline Analysis of Landmark COVID-19 Vaccine Study. Retrieved April 1, 2021, from https://www.businesswire.com/news/home/20210401005365/en/

[2] Liu et al., (2021). Neutralizing Activity of BNT162b2-Elicited Serum. NEJM, DOI: 10.1056/NEJMc2102017.

[3] Eric Topol. Retrieved April 1, 2021, from https://twitter.com/EricTopol/status/1377637894513324040

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