Booster Effectiveness Wanes After 4 Months, Study Shows

February 14, 2022

The study shows that the Pfizer/BioNTech and Moderna COVID-19 vaccine boosters lost some effectiveness after four months but still did a good job of keeping people out of hospitals during the Omicron surge.

The study found that at the time when the Omicron variant was dominant, the vaccines were 87% effective against emergency room visits and 91% effective against hospital admissions two months after revaccination. Four months after revaccination, the effectiveness had dropped to 66% for ER visits and 78% for hospital admissions.

A study published in CDC Weekly Morbidity and Mortality Report reviewed 241,204 emergency room visits and 93,408 hospital admissions across 10 states from August 2021 to January 22, 2022. The CDC said about 10% of people were boosted and more than half of those hospitalized were over 65.

The study did not come as a surprise because previous studies have shown that the effectiveness of the vaccine and booster vaccine declines over time, but it appears that the effectiveness of the booster vaccine against the Delta variant was higher than against Omicron, the CDC said. The highly contagious Omicron variant currently accounts for nearly 100% of COVID cases in the United States. Conclusions about the period when Omicron dominated were based on a small sample of fewer than 200 patients who received a booster at least four months ago.

Overall, the study provided further evidence that vaccines work and keep people out of the hospital, said Michael Saag, an infectious disease physician at the University of Alabama at Birmingham.

“Oddly enough, I see very few people who die after booster therapy,” he said. Associated Press. “Vaccines still work.”

In a separate report released Friday, the CDC changed its guidance on booster therapy for people with weakened immune systems. These people should be revaccinated three months after the Pfizer or Moderna primary series, not five months. agency said.

Approximately 7 million American adults are considered immunocompromised. Kaiser Health News has been reported, to include people with certain medical conditions that impair their immune response or who are taking immunosuppressive drugs due to organ transplants, cancer, or autoimmune diseases. The CDC recommended a fourth shot for immunocompromised people in October.

The CDC also changed its guidance for immunocompromised people who received a single dose of the Johnson & Johnson vaccine, saying they should receive a second dose 28 days later and then receive a booster dose of one of the mRNA vaccines. In addition, the CDC has stated that people do not need to delay COVID-19 vaccination after receiving monoclonal antibodies or convalescent plasma.

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