Pfizer Vaccine Effectiveness Drops To 84 Percent After Six Months, Study Finds

An anonymous reader quotes a report from The Hill: The effectiveness of the Pfizer-BioNTech COVID-19 vaccine fell from 96 percent to 84 percent over six months, according to data released on Wednesday. The preprint study funded by the companies determined that the vaccine's effectiveness reached a high point of 96.2 percent within two months after the second dose. But the efficacy 'declined gradually' to 83.7 percent within six months, with an average decrease of about 6 percent every two months. But even with the slip in efficacy, the data indicates the vaccine offers protection six months later.

The ongoing study with more than 44,000 participants across the Americas and Europe determined the vaccine was overall 91.1 percent effective, after 81 cases emerged among the vaccinated and 873 among those who received the placebo. The efficacy of the vaccine against severe disease including hospitalizations remained high, at 97 percent. Researchers will continue to observe participants of the study up to two years and combined with 'real-world' data 'will determine whether a booster is likely to be beneficial after a longer interval.' If the efficacy continued to decrease at the current rate, it could fall below 50 percent within 18 months, suggesting that booster shots could be needed.

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