2nd dose of J&J COVID-19 vaccine results in stronger protection, company says

A second dose of Johnson & Johnson's COVID-19 vaccine given two months after the first leads to stronger protection, according to the company.

A second dose of Johnson & Johnson's COVID-19 vaccine given two months after the first leads to stronger protection, according to the company.

The new data, announced in a press release, adds to a growing body of evidence suggesting that booster shots could enhance vaccine protection against breakthrough infections -- though experts agree all three vaccines are still doing their job to protect against more serious illness.

Compared to the Pfizer and Moderna vaccines, Johnson & Johnson's single-shot vaccine always had slightly lower efficacy. Peak efficacy from the two-shot Pfizer and Moderna vaccines was 95% and 94%, respectively, against symptomatic illness.

But two Johnson & Johnson shots, given two months apart, resulted in a similarly high effectiveness level: 94% protection against any symptomatic infection in the U.S., and 100% against severe disease.