(The Hill) — People who received the single-shot Johnson & Johnson COVID-19 vaccine are at higher risk of serious illness and hospitalization than those who received an mRNA vaccine, so they should seriously consider getting a booster dose of either Pfizer or Moderna’s shot, according to new Centers for Disease Control and Prevention (CDC) data released Tuesday.

Health officials first allowed people to mix and match booster shots last fall, but there’s been very little data on the real-world effectiveness of different strategies. The CDC study of ten states during the height of the omicron wave found that people who received a single J&J dose combined with an mRNA booster shot had better protection against severe outcomes than those with just the J&J dose. 

A single J&J dose provided only 31% protection against hospitalization. A booster dose of the J&J vaccine was better than a single dose, but people with three doses of mRNA vaccines had the best protection, with 90% effectiveness.

The findings against emergency department visits were similar to hospitalizations. A single J&J dose was only 24% effective against urgent care/emergency room visits. Adding an mRNA booster resulted in 79% effectiveness, while three mRNA shots were 83% effective. 

The study showed that any booster shot is better than none, but the CDC said an mRNA booster is strongly suggested. It analyzed data from more than 80,000 emergency room or urgent care visits, and more than 25,000 hospitalizations among adults with COVID-19-like illness in 10 states, from mid-December to March 7. The data were released the same day the Food and Drug Administration authorized a second booster dose of an mRNA vaccine for 50 years old and older, as well as severely immunocompromised people over the age of 12. 

Roughly 17 million people have received the Johnson & Johnson vaccine. While it was initially hailed as a game-changer, the shot has struggled to gain a foothold in the U.S. and is much more popular overseas. The vaccine has been linked to a rare but severe type of blood clot which led to the product’s pause for 10 days last spring. Usage dropped considerably after the 10-day pause was lifted. Supply chain issues and reports about lower effectiveness also served to tamp down usage.

Last December, CDC said providers should offer the Moderna and Pfizer COVID-19 vaccines rather than Johnson & Johnson’s because of the increased risk of blood clots. But the company has pointed to recent evidence that its vaccine is holding up better over time than the mRNA shots.

A study published in the JAMA Open Network journal, funded by Janssen Research and Development, found the vaccine was 76% effective against infection and 81% effective at preventing hospitalization after six months. However, the study was conducted when delta was the primary variant, not omicron.