A pharmacist at the Hartford Hospital in Hartford, Connecticut, fills a syringe with the Johnson & Johnson COVID-19 vaccine.
  • Some experts who got Johnson & Johnson's one-dose vaccine are topping it up with a dose of Pfizer or Moderna.
  • They did it for extra protection against the fast-spreading Delta coronavirus variant, they said.
  • The FDA and CDC don't recommend getting an extra shot, after a J&J vaccine or otherwise.
  • For more stories visit Business Insider.

Some experts who got Johnson & Johnson's one-dose vaccine are trying an extra shot of Moderna or Pfizer's vaccines to try to protect against the fast-spreading Delta coronavirus variant.

Officials have not recommended getting a booster shot after J&J's vaccine or any other vaccine, and two experts said everyone should wait for more data.

Angela Rasmussen, a virologist at the University of Saskatchewan, Canada, said on Twitter Tuesday that she got the Pfizer vaccine to "top off" the J&J vaccine she received in April.

Rasmussen said that the rise of the Delta variant in the UK- where more than 95% of new infections are caused by Delta - showed the "crucial importance" of getting as many people vaccinated as possible.

Rasmussen said that we don't know whether an extra vaccine dose after a J&J shot boosts protection against variants, and the Food and Drug Administration (FDA) or CDC haven't made any recommendations. But it was likely to work, given that boosters work for nearly every other vaccine in use, she said.

"We shouldn't wait to make recommendations about this," she said.

Rasmussen encouraged people who'd had J&J's shot, especially those living in communities with low vaccination rates, to speak with healthcare providers about getting an extra dose.

Dr. Anthony Fauci, President Joe Biden's chief medical adviser, said Wednesday that the Delta variant accounted for more than 20% of new infections in the US and was the "greatest threat" to the nation's efforts to eradicate Covid-19.

There's no data on how well J&J's vaccine works against the Delta variant. More than 9 million Americans have been given the single dose vaccine, according to the Centers for Disease Control and Prevention (CDC).

Jason Gallagher, clinical professor in infectious diseases at Temple University's School of Pharmacy, told Reuters Monday that he got J&J's vaccine in a trial in November, and recently had a dose of Pfizer-BioNTech's Covid-19 vaccine.

Gallagher said he was concerned about data that suggesteda single shot of either Pfizer or AstraZeneca's vaccine was only 33% effective against symptomatic Covid-19 caused by the Delta variant. "So I took the plunge," he said.

Professor Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, said in a tweet on Thursday that adding a second J&J dose, or an extra shot of Pfizer or Moderna vaccines, could provide broader protection against variants, "but we need data and CDC-FDA guidance."

Dr. John Beigel, associate director for clinical research at the National Institute for Allergy and Infectious Disease (NIAID), told Reuters Monday that J&J recipients should wait for more data.

Get the best of our site emailed to you every weekday.

Go to the Business Insider front page for more stories.