One year after the launch of mass vaccination against COVID-19, inactivated virus vaccines accounted for part of the doses administered worldwide. Now, a giant observational study conducted in Brazil and co-directed by Fiocruz and the Barcelona Institute for Global Health (ISGlobal), an establishment supported by the “la Caixa” Foundation, shows that, in other people who first received two doses of the inactivated CoronaVac vaccine, an mRNA booster gives significantly greater coverage against mild and severe COVID-19 than a booster with the same vaccine. These findings, published in Nature Communications, have vital implications for guiding reinforcement methods in countries where most of the population has received inactivated virus vaccines.
COVID-19 vaccination has been shown to be very effective in protecting against serious illness and death. However, the efficacy of vaccination number one (i. e. the initial two doses) was reduced with the arrival of new variants of concern, Omicron added, justifying a booster dose.
Most vaccine effectiveness studies have focused on mRNA and adenoviral vaccines, inactivated virus vaccines have been widely used, especially in low- and middle-income countries. In fact, in January 2022, they are part of the doses administered worldwide. “Reinforcements in populations that have received inactivated vaccines are essential to advise long-term vaccination methods in these countries,” says Otavio Ranzani, ISGlobal researcher and first author of the study.
In this study, Ranzani and colleagues evaluated the efficacy of booster with an inactivated virus vaccine (CoronaVac) or with an mRNA vaccine (Pfizer) in Brazilian adults who first received two doses of CoronaVac. The analysis, which included nearly 1. 4 million pairs of cases and controls, was conducted between December 2021 and April 2022, an era in which Omicron BA. 1 predominated, and compared to an era in which Delta predominated.
The strength of our observational study lies in the length of the giant pattern and geographical coverage, which covers Brazil’s 5,570 municipalities. “
The effects show that the number one vaccination with two doses of the CoronaVac vaccine provided almost no coverage against symptomatic diseases through Omicron, and 40-50% coverage against severe diseases. Stimulation with CoronaVac did not confer additional coverage against symptomatic diseases and further moderated coverage against serious diseases (74% and up to 40-50% for other people over 75 years of age). In addition, this coverage fades in the next 4 months. In contrast, an mRNA booster provided superior coverage compared to symptomatic and severe disease (56. 8% and 86%, respectively) and gave the impression of lasting at least 4 months.
“Our findings have immediate implications for retirement management methods in the context of the Omicron variant,” says Ranzani. They show that, in Americans who first won inactivated vaccines, a heterologous booster (in this case with an mRNA vaccine) gives a really extensive construct in protection, even in the elderly.
Barcelona Institute for Global Health (ISGlobal)
Ranzani, O. T. , et al. (2022) Efficacy of an inactivated Covid-19 vaccine with homologous and heterologous Omicron boosters in Brazil. Communication Nature. doi. org/10. 1038/s41467-022-33169-0.
News-Medical. net – An AZoNetwork website
Owned and operated through AZoNetwork, © 2000-2022