COVID-19 Booster Shots Less Effective Over Time, But Still Offer Protection

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COVID-19 Booster Shots Less Effective Over Time, But Still Offer Protection

COVID-19 vaccine “booster” shots offer the greatest protection against the viral infection soon after people receive them, but are still effective at reducing hospitalization after four months or longer, according to new data released by the U.S. Centers for Disease Control and Prevention (CDC).

People with diabetes have been disproportionately harmed by COVID-19 throughout the pandemic, and many people with diabetes also have other health conditions that put them at risk for severe disease if they develop the viral infection. Among people with diabetes, the risk for poor outcomes related to COVID-19 — like hospitalization, admission to the intensive care unit (ICU), and death — is linked to your long-term history of blood glucose control, which may reflect the damage that elevated blood glucose can cause to many of the same organ systems that COVID-19 also potentially damages. Because of the higher risk that people with diabetes face from COVID-19, diabetes was among the health conditions that qualified for priority access to COVID-19 vaccines and booster shots.

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Right now, booster shots are recommended for anyone who received the original doses of the COVID-19 vaccine — meaning that anyone age 12 or older qualifies. But as the virus itself has evolved through several variants, there have been questions among both researchers and the general public about how effective these extra doses of the vaccine actually are at protecting people from infection, as well as complications of COVID-19. So newly released data from the CDC was highly anticipated, and the results are likely to be seen as both reassuring and disappointing in different ways.

COVID booster effectiveness

First, the data shows that among people ages 18 and older who received a booster shot in 10 U.S. states between late September 2021 and early February 2022, the cumulative series of vaccines was 91% effective at protecting against hospitalization from the Omicron variant of COVID-19 during the first two months after the booster shot. But after four months, this efficacy rate dropped to 78% — still a high degree of protection, but by no means complete protection against hospitalization. The data also showed that the cumulative series of vaccines was less protective against Omicron than against the previous Delta variant. Among all hospitalizations for COVID-19 during the study period — during both the Delta and Omicron periods — 43% of patients were unvaccinated, 45% had received only the original vaccine series, and 12% had received a booster shot, as noted in a Healio article on the CDC report. Overall, 89% of hospitalizations took place during the Delta period.

The report’s authors concluded that these findings reinforce the importance of getting a COVID-19 booster shot, since the original vaccine series alone no longer provides adequate protection against the viral infection. But the results also suggest that additional booster shots should be considered in future recommendations, since the protection offered by a single booster shot may not be enough to prevent widespread serious illness — and overwhelmed hospitals — from either Omicron or future variants of COVID-19.

Want to learn more about coronavirus and diabetes? Read our latest COVID-19 updates.

Quinn Phillips

Quinn Phillips

Quinn Phillips on social media

A freelance health writer and editor based in Wisconsin, Phillips has a degree from Harvard University. He is a former Editorial Assistant for Diabetes Self-Management and has years of experience covering diabetes and related health conditions. Phillips writes on a variety of topics, but is especially interested in the intersection of health and public policy.

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