Although Johnson & Johnson's (J&J) Covid-19 vaccine has been considered less effective compared to other vaccines, new data suggests that it is now protecting against infection and severe illness just as well as the mRNA vaccines—if not better, Apoorva Mandavilli writes for the New York Times.

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Background

When J&J's vaccine was first rolled out, it was billed as a "one and done" shot compared with the two-dose series needed for both Pfizer-BioNTech's and Moderna's mRNA vaccines. Although the J&J vaccine's efficacy appeared to be lower than the mRNA vaccines, it was still protective against severe disease and had other advantages, such as being easier to store.

However, since then, J&J's vaccine has been linked to a rare but serious blood clotting disorder and experienced production mishaps that contaminated millions of doses. In addition, federal health authorities in December recommended Pfizer-BioNTech's and Moderna's vaccines over J&J's, citing concerns about potential clotting risks.

Currently, around 17 million Americans have received the J&J vaccine, much fewer than the 92 million Americans who have received either of the mRNA vaccines.

J&J's vaccine holds its own against mRNA vaccines, data suggests

According to Mandavilli, recent data suggests that the gap in protection between the J&J and mRNA vaccines appears to be narrowing. In fact, the J&J vaccine may be performing slightly better on certain metrics.

"We've been aware that [J&J] has been kind of downgraded in people's minds," said Linda Gail-Bekker, director of the Desmond Tutu HIV Center at the University of Cape Town. "[But] it punches above its weight for a single-dose vaccine.

Last June, cumulative data from CDC showed that J&J recipients had the highest rates of breakthrough infections compared with the Moderna and Pfizer-BioNTech vaccine recipients. But now, all three vaccines seem to be equally protective against coronavirus infections.

Based on the latest available data through Jan. 22, unvaccinated people were 3.2 times more likely to be infected than those who received one dose of J&J's vaccine. In comparison, unvaccinated people were 2.8 times more likely to be infected than people with two doses of Moderna's vaccine and 2.4 times more likely to be infected than those with two doses of Pfizer-BioNTech's vaccine.

Overall, this suggests that the J&J vaccine "appeared to be somewhat more protective against infection than the two alternatives," Mandavilli writes. Similar results were also found among Americans who had been boosted, although the data did not indicate which type of booster was received.

In addition, new data from South Africa found that two doses of J&J's vaccine were 75% effective against hospitalization from the omicron variant—similar to the protection offer by Pfizer-BioNTech's vaccine.

Currently, it is not clear why protection from J&J's vaccine seems to have improved over time, although scientists have posited some potential explanations, Mandavilli writes.

For example, antibodies produced by the J&J vaccine may decline more slowly than those produced by other vaccines. These antibodies may also have become more sophisticated over time through a process called affinity maturation. Some researchers have also suggested that J&J's vaccine provided more robust protection against the omicron variant, which was responsible for the surge in infections over the last few months.

According to Larry Corey, an expert in vaccine development at the Fred Hutchinson Cancer Research Center, these findings indicate that J&J's vaccine may deserve closer assessment. "This [adenovirus] vaccine platform may have some surprising characteristics that we hadn't anticipated," he said. " ... It has much longer durability than almost any other platform that we've worked with."

More data is needed to determine 'the best vaccine regimen for the future,' experts say

However, not all researchers are convinced that the J&J vaccine has improved over time. According to Natalie Dean, a biostatistician at Emory University, J&J's vaccine may only appear to be more effective now since many recipients developed breakthrough infections early on, which boosted their immunity. "They may have a different immunity profile," she said.

In particular, Dean noted that while the infection rate is now lower among unboosted J&J recipients compared with unboosted mRNA recipients, the death rate among J&J recipients remains slightly higher.

However, Dan Barouch, a virologist at Beth Israel Deaconess Medical Center who collaborated with J&J on its vaccine, said the differences in death rates are not huge and even disappeared among those who were boosted. Since CDC's data on deaths only goes through Jan. 1, Barouch said J&J's edge when it comes to death rate may only become apparent when data from February or March is available.

Overall, Dean said a clearer comparison of the different Covid-19 vaccines would require more data, particularly on individual factors such as previous infections and high-risk conditions, rather than just age-adjusted overall numbers from CDC. More data on different combinations of vaccine may also help clarify which is the most effective and safest over time, she added, although new variants could impact which vaccines are most effective.

"I do keep a very open mind about what could end up being the best vaccine regimen for the future," Dean said. (Mandavilli, New York Times, 3/15)