Study finds Pfizer vaccine works at 90% efficacy for six months

pfizer vaccine six months, delta variant
© Rodrigo Fernández

The study, published in The Lancet, finds that two doses of the Pfizer vaccine are 90% efficient for six months – decreasing to 47% after that time period

In August, an 800,000 person study found that the Pfizer vaccine is safe in a real-world setting. Currently, the COVID pandemic continues – especially in places that don’t have access to the vaccine. In others, vaccine hesitancy lingers and impacts how willing people are to get vaccinated.

Among this, there is a debate about whether booster doses are necessary for the general population. In August, the WHO even asked richer countries to hold-off on buying more doses.

Dr Tedros Adhanom Ghebreyesus, WHO Director-General, said: “We need an urgent reversal from the majority of vaccines going to high-income countries, to the majority going to low income countries.”

Efficacy falls to 47% after six months

Now, fresh research seems to suggest that two doses of Pfizer vaccine can protect against hospitalisation from COVID, at 90%, for six months. After six months, the rate begins to decline to 88% after one month. When a full six months have passed, efficacy falls to 47%.

The team used data from 3,436,957 electronic health records, in Southern California. The data was taken between 4 December, 2020, to 8 August, 2021.

Dr Sara Tartof, lead author and Kaiser Permanente Southern California Department of Research & Evaluation, said: “Our study confirms that vaccines are a critical tool for controlling the pandemic and remain highly effective in preventing severe disease and hospitalization, including from the delta and other variants of concern.

“Protection against infection does decline in the months following a second dose.”

What about how Pfizer works on variants?

According to the variant-specific analysis done by the team, a double-dose of the vaccine holds up well against Delta.

Two doses of Pfizer provide 93% protection against Delta variant infections, falling to 53% after four months. Interestingly, the Pfizer vaccine creates stronger protection against the Delta variant.

Effectiveness against other variants at one month after receiving two doses was 97% and declined to 67% after four months.

Dr Luis Jodar, Senior Vice President and Chief Medical Officer, Pfizer Vaccines, said: “Our variant-specific analysis clearly shows that the BNT162b2 vaccine is effective against all current variants of concern, including delta. COVID-19 infections in people who have received two vaccine doses are most likely due to waning and not caused by delta or other variants escaping vaccine protection.”

Read the full study here.


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