- The efficacy of Pfizer's coronavirus vaccine steadily declines to about 84% about six months after a second dose, according to CEO Albert Bourla.
- Data from Israel shows the waning immunity also erodes protection from severe illness.
- The vaccine's initial studies showed it protected people 100% of the time against hospitalization, but that falls to low 90% and mid-to-high 80% after six months, he said.
The effectiveness of Pfizer's Covid-19 vaccine steadily declines over time, dropping to about 84% for vaccinated people about four to six months after getting their second dose, according to CEO Albert Bourla.
The comments, made on Wednesday on CNBC's "The Exchange," are based on the findings of a new company-funded study that has yet to be peer reviewed. It comes as the drugmaker clashes with U.S. health officials over the need for a third Covid vaccine dose to boost immunity protection.
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The study found the vaccine's effectiveness was strongest, at 96.2%, between one week and two months after receiving the second dose. It declined an average of 6% every two months, according to the study, which signed up more than 44,000 people across the U.S. and other countries. The efficacy after "four to six months was approximately 84%," Bourla said.
"We have seen also data from Israel that there is a waning of immunity and that starts impacting what used to be what was 100% against hospitalization. Now, after the six month period, is becoming low 90s and mid-to-high 80s," Bourla said.
"The good news is that we are very, very confident that a third dose, a booster, will take up the immune response to levels that will be enough to protect against the delta variant," the executive added, referring to the highly contagious virus strain that's dominant in the U.S. and other countries around the globe. It's not uncommon for vaccines to decline in effectiveness over time, Bourla stressed, adding there's precedent for three-dose vaccines for other diseases.
Pfizer plans to formally submit data to U.S. regulators about the benefits of a third Covid vaccine dose by mid-August, Bourla said.
Earlier this month, when Pfizer first announced its plans, the Food and Drug Administration and the Centers for Disease Control and Prevention issued a joint statement that pushed back on the company, saying "Americans who have been fully vaccinated do not need a booster shot at this time."
The CDC and the World Health Organization don't recommend Covid booster shots at this time.
Dr. Kate O'Brien, WHO's director of immunization, vaccines and biologicals, said Wednesday the organization is still researching whether a booster shot is needed to increase protection.
"We're very clear on this, there's not enough information to provide a recommendation at this point," O'Brien said in a Q&A interview posted on the organization's social media accounts. "Again, this is a very hot topic, and there's a lot of research going on to be able to provide an evidence-based recommendation."
The results of Pfizer-backed study surfaced a day after the CDC reversed course on its prior guidance and recommended fully vaccinated Americans who live in areas with high Covid infection rates begin to wear face masks indoors again.
Coronavirus cases have jumped nationwide in recent weeks, a surge public-health officials attribute to the delta variant. While officials say the majority of Covid hospitalizations and deaths are in unvaccinated people, the delta variant is so contagious that vaccinated individuals can transmit the virus as easily as unvaccinated people, even in asymptomatic cases, CDC Director Rochelle Walensky said Tuesday.