A third booster dose of the COVID-19 vaccine was associated with a 90% reduction in deaths in people with multiple health conditions compared to two doses, according to a study conducted in Hong Kong.
Research published in the Canadian Medical Association Journal compared data from people aged 18 or older with two or more chronic conditions, such as high blood pressure, diabetes and chronic kidney disease, who received a third dose between November 2021 and March 2022, compared with people who received only 2 doses.
Esther Chan of The University of Hong Kong says “We found a substantially reduced risk of death related to COVID-19 in adults with multimorbidity who received a homologous booster dose of BNT162b2, an mRNA vaccine, or CoronaVac, an inactivated whole virus vaccine, these results support the efficacy of vaccine boosters on two different technology platforms in reducing mortality in people with multimorbidity during the Omicron epidemic”.
When the Omicron variant (BA.2) epidemic hit Hong Kong in late 2021, the city reported the world’s highest death rate from COVID-19 per population of 7.5 million people, the researchers said.
From November 11, 2021, the elderly, healthcare workers and other priority groups could receive a booster dose of either the BNT162b2 mRNA vaccine (Pfizer-BioNTech) or CoronaVac (Sinovac).
From 1 January 2022, all others became eligible, resulting in more than three million people receiving booster benefits in the first four months of 2022.
Francisco Lai, first author and researcher at the University of Hong Kong says “Our findings suggest that this early, massive public health intervention plausibly played a key role in reducing mortality in the midst of the epidemic, especially among people living with multimorbidity”.
The study included 120,724 Pfizer-BioNTech vaccine recipients (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 researchers said.
The findings highlight the potential benefit of booster vaccination, particularly in vulnerable populations living with multimorbidity, and support the recent focus on the elderly and those with chronic disease for future booster doses of SARS-CoV-2 vaccines after the first booster” The study will add to the evidence base that boosting provides strong protection against death from COVID-19, the researchers added.
