Booster Shots Protect Against Severe Covid for at Least Six Months, Study Finds

A Covid-19 vaccine booster shot protects people from becoming severely ill or dying and its efficacy lasts for six months, according a study published in the Journal of the American Medical Association, underscoring the importance of additional jabs as the world moves to coexist with the virus. The mRNA booster vaccines -- made by drugmakers Pfizer Inc. and BionTech SE, or Moderna Inc. -- were most effective in cutting the rate of people with severe Covid, scoring an estimated 87%, and there was no evidence of their effect waning within six months, the study found. Inactivated booster vaccines by Sinovac Biotech Ltd. and Sinopharm Group Co. also cut the chance of severe illness by about 70%. Severe Covid was defined in the research as requiring oxygen supplementation, intensive care or death.