COVID death risk decreases 90% after booster shot, study finds

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In a study from The University of Hong Kong, scientists found a booster (third) dose of a SARS-CoV-2 vaccine was linked to a 90% reduction in death in people with multiple health conditions compared to 2 doses.

These results support the effectiveness of booster doses of vaccines of 2 different platforms in lowering death risk amid the Omicron epidemic.

As the Omicron (BA.2) variant epidemic hit Hong Kong in late 2021, the city reported the highest COVID-19 mortality rate worldwide relative to its population of 7.5 million people.

Since November 11, 2021, older people, health care professionals and other priority groups were able to receive a booster dose of either the BNT162b2 mRNA (Fosun-BioNTech, equivalent to Pfizer-BioNTech outside China) or CoronaVac (Sinovac) vaccine.

As of January 1, 2022, all others were eligible, resulting in more than 3 million people receiving booster doses in the first 4 months of 2022.

In the study, the team compared data on people aged 18 years or older with 2 or more chronic conditions, such as high blood pressure, diabetes and chronic kidney disease, who received a booster (third) dose compared to people who received only 2 doses.

They tested 120 724 recipients of the Pfizer-BioNTech vaccine (87 289 who received a booster) and 127 318 CoronaVac recipients (94 977 who received a booster).

There were more deaths among CoronaVac recipients than Pfizer-BioNTech recipients.

The findings suggest that this timely, massive public health measure has plausibly played a pivotal role in lowering the mortality rate amid the epidemic, especially among people living with multimorbidity.

The robust results will contribute to the evidence base that getting boosted provides strong protection against death from COVID-19.

The study was conducted by Dr. Esther Chan et al and published in CMAJ (Canadian Medical Association Journal).

If you care about COVID, please read studies about Vitamin D deficiency linked to severe COVID-19, and low-sodium plant-based diets may prevent COVID-19 better.

For more information about COVID, please see recent studies about new evidence on rare blood clots after COVID-19 vaccination, and results showing zinc could help reduce COVID-19 infection risk.

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