Pfizer’s coronavirus vaccine is 90% effective at preventing hospitalization, with no waning protection from hospital admission for up to six months, a new study found.
The study, published in the Lancet, found that even amid the delta variant, the vaccine manufactured by Pfizer and BioNTech was highly effective against hospitalization from the coronavirus until about six months after an individual was fully vaccinated.
Reports began to surface in recent months questioning the effectiveness of coronavirus vaccines against the variant, as delta made its way around the world this summer. But the emergence of the delta variant may not be the primary driver of reported declines in protection from the coronavirus, the report suggests. The surge of the delta variant in countries like the U.S. and Israel coincided with the time period during which high-risk individuals, or those who likewise received a coronavirus vaccine early on for occupational reasons, were approaching six months since completing their coronavirus vaccinations, the report notes, making waning vaccine-induced immunity “an important factor to consider in the context of reported declines in effectiveness.”
Conducted by researchers at Pfizer and Kaiser Permanente who analyzed electronic health records of more than 3 million members of Kaiser Permanente Southern California between December 2020 and August 2021, the study suggests that reduced effectiveness over time is “likely to be primarily due to waning vaccine effectiveness rather than the delta variant escaping vaccine protection,” the report notes.
But overall protection from infection did decline over time, the report found. Fully vaccinated individuals saw 88% effectiveness against coronavirus infection during the first month after vaccination, which fell to 47% after five months.
The study comes amid debate over when booster shots should be made available to the general population. The report notes that the findings underscore the importance of monitoring vaccine effectiveness overtime and “suggest that booster doses are likely to be needed to restore the initial high amounts of protection” observed early on in the vaccination program.
The FDA authorized booster shots of Pfizer’s vaccine for certain at-risk populations last month, while Moderna and Johnson & Johnson’s vaccine recipients await approval. U.S. health officials said they believed J&J and Moderna recipients would need a booster shot as well but opted to wait for additional data. On Tuesday, J&J announced that it has asked the Food and Drug Administration for emergency use authorization of its coronavirus booster shot in people ages 18 and older, while Moderna did the same last month.