CDC study shows booster shots provide protection against severe illness

by mcardinal

Lauren Dempsey, MS in Biomedicine and Law, RN, FISM News 

 

A recent CDC study that was released Friday indicates that booster shots are effective at preventing severe illness or hospitalization from SARS-CoV-2 infection, even as the Omicron variant is the primary variant circulating in the United States.

This new research was released as the CDC continues to double down on the importance of vaccination. 

Rochelle Walensky, the CDC director said in an interview that “there are still millions of people who are eligible for a booster dose and have not yet received one,” and added “as we continue to face the Omicron variant – representing over 99% of infections in the United States today – I urge all who are eligible to get their booster shot, to get it as soon as possible.”

The study’s data suggests that booster shots are 90 percent effective at preventing hospitalization, especially in persons who are aged 50 and older. The study evaluated millions of Americans in 25 U.S. jurisdictions between April 4 and December 25, 2021. Researchers evaluated the case counts in fully vaccinated, boosted and unvaccinated individuals. The study used real-life data to examine the impact that booster shots have against the Omicron variant. Individuals that tested positive in the vaccinated cohort were included only if they were more than 14 days post-injection, and those that were partially vaccinated were excluded from the study. 

The CDC determined a COVID-19 related death to be any individual that had a positive diagnosis and whose local health authority made the determination that the diagnosis was in any way related to death. This includes anyone with COVID-19 as an underlying cause or contributing factor listed on the death certificate. 

The data revealed that the case rates and deaths per 100,000 were higher during the Delta wave after the emergence of the Omicron variant when compared to pre-Delta rates. It also showed that the cases were higher among the unvaccinated when compared to fully vaccinated persons during this time period.

Additionally, in the time period between October and November of 2021 fully vaccinated individuals that also received a booster shot had the lowest case rates and mortality rates.

The study authors, however, did admit there are multiple limitations associated with the study. Limitations they listed included: researchers could not differentiate booster doses from primary doses in immunocompromised individuals; there were differences in testing, immunity, waning vaccine efficacy, and changes in testing and reporting methods based on jurisdiction; variant prevalence varied by jurisdiction; the incident rate ratios may have been affected by misclassifications of data; and the information from this study only represents 62% of the United States, and “may not be generalizable.”

While the CDC has already admitted that many positive cases of hospitalized persons are incidental findings, this study does show that among high-risk populations a booster may be effective in preventing severe illness. This is especially true since the vaccines do not prevent infection or the spread of the virus.

Dr. Walensky explained that the “data highlights two important points. First, those who remain unvaccinated are at a significantly higher risk for infection and severe COVID-19 disease,” and “second, protection against infection and hospitalization with the Omicron variant is highest for those who are up to date with their vaccination, meaning those who are boosted when they’re eligible.” 

However, this seems to contradict a recent Israeli study that indicates a fourth dose of COVID-19 vaccines provide limited protection against the Omicron variant and does very little to prevent the spread of the virus. Sheba Medical Center’s clinical trial found that while there was a slightly higher boost of antibodies following a third vaccine, this boost did not prevent the spread or limit infection of COVID-19. The study evaluated a fourth dose of COVID-19 vaccines in their medical workers who received Pfizer-BioNTech or Moderna vaccines. 

Dr. Gili Regev-Yochay, director of the hospital’s infection disease unit, said, “Despite increased antibody levels, the fourth vaccine only offers a partial defense against the virus,” adding that “the vaccines, which were more effective against previous variants, offer less protection versus Omicron.”  

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