How Effective Is Pfizer-BioNTech Vaccine Against COVID-19 Variants?
While it has been known that COVID-19 vaccines appear to be less effective against the so-called South African variant of SARS-CoV-2, a new Israeli study has heightened those concerns. Researchers found the Pfizer-BioNTech vaccine had reduced vaccine effectiveness under different dosage/timing conditions, as demonstrated by breakthrough cases. Here is more information.
TEL AVIV, ISRAEL – An Israeli study is raising concerns about increased SARS-CoV-2 breakthrough rates with the so-called South African variant in those who received the Pfizer-BioNTech vaccine.
In a preprint article which has not been peer-reviewed, researchers from Tel Aviv University and Clalit, the largest health-care organization in Israel, pointed out that the BNT162b2 mRNA vaccine from the two companies has demonstrated high protection levels. Still, they wrote in the medRXiv that “apprehension exists that several variants of concerns (VOCs) can surmount the immune defenses generated by the vaccines.”
They add that, while neutralization assays have revealed some reduction in neutralization of VOCs B.1.1.7 and B.1.351, the relevance of these assays in real life have remained unclear.
In response, researchers performed a case-control study examining whether about 400 BNT162b2 vaccinees with documented SARS-CoV-2 infection were more likely to become infected with B.1.1.7 or B.1.351 compared with about the same number of unvaccinated individuals.
Results indicate that vaccinees infected at least a week after the second dose were disproportionally infected with B.1.351 for an odds ratio of 8:1. “Those infected between two weeks after the first dose and one week after the second dose, were disproportionally infected by B.1.1.7 (odds ratio of 26:10), suggesting reduced vaccine effectiveness against both VOCs under different dosage/timing conditions,” the authors wrote. “Nevertheless, the B.1.351 incidence in Israel to-date remains low and vaccine effectiveness remains high against B.1.1.7, among those fully vaccinated.”
The researchers add, “These results overall suggest that vaccine breakthrough infection is more frequent with both VOCs, yet a combination of mass-vaccination with two doses coupled with non-pharmaceutical interventions control and contain their spread.”
In a press release at the beginning of April, Pfizer and BioNTech said recent data supported previous results from immunogenicity studies demonstrating that their vaccine induced “a robust neutralizing antibody response” to the South African B1.351 variant, adding that, “although lower than to the wild-type strain, it does not appear to affect the high observed efficacy against this variant.”
That press release included updated topline results from analysis of 927 confirmed symptomatic cases of COVID-19 observed in the companies’ Phase 3 study through March 13, 2021. It found the Pfizer-BioNTech COVID-19 vaccine to be 91.3% effective against COVID-19, measured seven days through up to six months after the second dose. It also was deemed 100% effective against severe disease as defined by the national Centers for Disease Control and Prevention and 95.3% effective against severe COVID-19 as defined by the FDA.