Pfizer says immunity can drop to 84% within four months in people who got its COVID-19 shot, further bolstering the company case for a booster

Market Watch/ By Jaimy Lee

The drug maker said this week that new data shows effectiveness can decline to about 83.7% four to six months after vaccination

The effectiveness of Pfizer’s COVID-19 shot can drop to 83.7% within four to six months after getting the second dose of its vaccine. This is the latest indication that vaccine-induced immunity to the virus can wane and some kind of boost may be necessary in the future.

New research published Wednesday as a preprint indicates that the Pfizer Inc.  shot provides 96.2% protection for the first two months, 90.1% effectiveness between the second and fourth months, and between 83.7% of protection for the fourth, fifth, and six months. 

“We will need a booster eight to 12 months from the second dose,” Pfizer CEO Albert Bourla said Wednesday, according to a FactSet transcript of the company’s second-quarter earnings call. 

The drug maker has been making the case for booster shots, citing limited data from its own clinical research and real-world data out of Israel, where Pfizer’s vaccine is the predominant shot in circulation.  “We do see—after six to eight months—more rapid waning concerning infections and mild to moderate symptoms,” Dr. Mikhail Dolsten, Pfizer’s chief scientific officer, said during the call. “Those are likely entirely, or to a large degree, dependent on antibodies and the drop in titer that we alluded to. If you raise it, you may have a good probability to reverse that waning.

Still, there’s no simple black-and-white answer to whether booster shots are needed at this time. One, there is no definitive data. The new Pfizer data is the most detailed so far, though the company plans to submit clinical data for a third dose to the Food and Drug Administration in early August.

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CDC Updates Mask Guidance

CNN has reported, "To prevent further spread of the Delta variant, the US Centers for Disease Control and Prevention updated its mask guidance on Tuesday to recommend that fully vaccinated people wear masks indoors when in areas with "substantial" and "high" transmission of COVID-19, which includes nearly two-thirds of all US counties. New unpublished data showing that vaccinated people infected with the Delta coronavirus variant can have as much virus as those who are unvaccinated is the primary driver for the CDC's latest mask guidance change, a source involved with the decision process told CNN. Overall, vaccinated people still play a small role in transmission and breakthrough infections are rare."