Pfizer Says Its Vaccine Starts Losing Efficacy After This Long

As time goes on, experts continue to collect data on how the protection provided by the COVID vaccines fares over longer periods. Pfizer, Moderna, and Johnson&Johnson have all found evidence that suggests their vaccines continue to provide substantial protection for up to six months, but there's still a question of what happens after that. Now, Pfizer is saying immunity may wane over time in the face of the more infectious Delta variant, and the company announced it would be seeking authorization for a third booster shot of its vaccine in August.

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In a July 8 announcement, Pfizer cited a study from the Israel Ministry of Health that found that vaccine efficacy "in preventing both infection and symptomatic disease has declined six months post-vaccination." Meanwhile, the vaccine seems to remain effective at preventing serious illness beyond six months. Pfizer also noted the additional challenge the Delta variant poses in conjunction with waning immunity. The July 5 study out of Israel concluded that the Pfizer vaccine is not as effective against the Delta variant as it is against other strains, The Wall Street Journal reported.

The study was done from early June to early July, while Israel was experiencing an outbreak caused by the Delta variant. Israel's Health Ministry reported that amid the surge, the Pfizer vaccine was only 64 percent effective against infection and 94 percent effective at preventing serious illness. This is a substantial drop from Pfizer's original efficacy, which was 94 percent effective against any infection and 97 percent effective at preventing severe illness.

In the statement, Pfizer noted that the findings in the Israel study are consistent with the company's ongoing analysis. "That is why we have said, and we continue to believe that it is likely, based on the totality of the data we have to date, that a third dose may be needed within six to 12 months after full vaccination," the statement reads.

Pfizer recipients remain highly protected against severe illness from COVID for six months, but per the statement, the emergence of variants and a natural decrease in efficacy against symptomatic disease are expected to occur, which could lead to the need for a third dose. "Based on the totality of the data they have to date, Pfizer and BioNTech believe that a third dose may be beneficial to maintain the highest levels of protection," the statement says.

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Pfizer's Mikael Dolsten, PhD, told the Associated Press that data from the company's booster shot study suggests that people's antibody levels could jump five- to 10-fold after a third dose. While Pfizer seems certain that they want to send out third shots, regulatory agencies aren't as convinced. Per CNN, the U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) have released a joint statement saying, "Americans who have been fully vaccinated do not need a booster shot at this time."

On June 9, the World Health Organization (WHO) also told CNN, "We don't know whether booster vaccines will be needed to maintain protection against COVID-19 until additional data is collected." The organization noted that there are "limited data available on how long the protection from current doses lasts and whether an additional booster dose would be beneficial and for whom."

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