Without published data on whether combining two different vaccines is safe and effective or backing from U.S. health regulators. Canada and some European countries are already allowing people to get two different COVID-19 shots.
CDC Director Rochelle Walensky warns that the debate centers on concerns over how protective the J&J shot is against the Delta variant first detected in India and now circulating widely in many countries. Delta, which has also been associated with more severe disease, could quickly become the dominant version of the virus in the United States.
“There’s no doubt that the people who receive the J&J vaccine are less protected against disease,” than those who get two doses of the other shots, said Stanford professor Dr. Michael Lin. “From the principle of taking easy steps to prevent really bad outcomes, this is really a no-brainer.”
J&J said it is testing whether the immune response from its vaccine is capable of neutralizing the Delta variant in a laboratory setting, but no data is available yet.
Both mRNA vaccines showed efficacy rates around 95% in large U.S. trials, while J&J’s vaccine was 66% effective in preventing moderate-to-severe COVID-19 globally when more contagious variants were circulating.