The CDC on March 29 greenlighted a second booster with mRNA COVID-19 vaccines for people who received Johnson & Johnson's vaccine as their primary dose and initial booster.
The move came shortly after the agency published data indicating three doses of Pfizer or Moderna's mRNA vaccines perform best, followed by the combination of a Johnson & Johnson vaccine and an mRNA booster. Johnson & Johnson recipients who got a second dose of the J&J shot had lower levels of protection against emergency room or urgent care visits and hospitalization.
"Adults who received a primary vaccine and booster dose of Johnson & Johnson's Janssen COVID-19 vaccine at least four months ago may now receive a second booster dose using an mRNA COVID-19 vaccine," the CDC said in a statement. The agency stopped short of explicitly recommending the second booster, saying those eligible may get it.
The CDC study is based on an analysis of 80,287 ED or urgent care visits and 25,244 hospitalizations across 10 states between December and March, a period when omicron was dominant.
When looking at the ability to prevent ER or urgent care visits, researchers found three mRNA shots was 83 percent effective, reflecting the highest levels of protection. Here's how other vaccine combinations stacked up in preventing ED visits:
One J&J dose: 24 percent
Two J&J doses: 54 percent
One J&J dose followed by an mRNA dose: 79 percent
In terms of protection against hospitalization, three mRNA doses were 90 percent effective. Here's how the other vaccine combinations stacked up against hospitalizations:
One J&J dose: 31 percent
Two J&J doses: 67 percent
One J&J dose followed by an mRNA dose: 78 percent