The vaccine against covid from Pfizer-BioNTech (BNT162b2) is “highly” effective in preventing hospitalizations caused by all variants of the coronavirus for at least six months, according to a study published by The Lancet on Tuesday.
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The study, carried out by the US health care company Kaiser Permanente Southern California (KPSC) and Pfizer, indicates that the efficacy of two doses of this preparation against hospitalizations remains at 90% during those 24 weeks, although it drops considerably after that period. .
After administering the full regimen, the efficacy of BNT162b2 is 88% during the first month, but falls to 47% after six months, highlights the research, which has tested the vaccine with different variants, including delta, considered as a contagious.
In this sense, the experts found that the drop in efficacy against infection over time of the preparation from the pharmaceutical company Pfizer has to do with its own decline, and does not mean that the virus “eludes” the protection offered by the vaccine. , as explained in a statement.
Delta variant became dominant
However, they note that the delta variant became the dominant variant in the middle of the study period, so they recommend that follow-up analyzes be carried out to measure the rate of decline of this variant with respect to other variants.
In total, the researchers examined 3,436,957 electronic health records from Kaiser Permanente Southern California (KPSC) from December 4, 2020 to August 8, 2021.
During this period, 5.4% of the individuals were infected with SARS-CoV-2 and, within this group, 6.6% were hospitalized, while the time elapsed between the first and second doses was, on average, between three and four months.
Analysis of the complete genomic sequence and viral lineage of 8,911 positive PCR tests determined that the delta variant comprised 28% of the total proportion of positive sequences.
Specifically, the proportion of positive cases attributed to the delta grew from 0.6% detected in April 2021 to almost 87% last July, which confirmed that this variant was already the dominant one in the United States.
Delta variant infections after two doses of Pfizer
The study highlights that the efficacy of BNT162B2 against infections caused by the delta variant after two doses was 93% during the first month, although it fell to 53% after four months.
Compared to other variants, the efficacy in the month after the complete regimen reached 97% and fell to 67% after four months.
“Our study confirms that vaccines are a key tool to control the pandemic and remain highly effective in preventing serious illness and hospitalizations, including delta and other worrisome variants,” says lead author Sara Tartof of the KPSC.
The expert acknowledges that protection against infection declines in the months after the second dose, but points out that the competent authorities are demanding more studies to determine whether booster doses of these vaccines should be administered “to all age groups.”
With information from EFE
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