Janssen’s “booster” vaccine.

Johnson & Johnson’s (JNJ) Janssen subsidiary came out today with long expected data that showed an improvement in protection with a second dose of its COVID vaccine. I have previously suggested this vaccine should have been offered as two doses in the first place.

The company said Tuesday, data from a Phase 3 trial and real-world evidence confirm that its single-shot COVID-19 vaccine offers strong and long-lasting protection against hospitalization and death. However, the company said further data now shows that a booster shot offers increased protection.

This two dose Phase 3 trial was in comparison to 390,000 people who got the J&J one-shot vaccine versus about 1.52 million unvaccinated people matched on age, sex, time, location, comorbidities and COVID-19 infection severity. The trial data have been submitted to the U.S. Food and Drug Administration and other regulators worldwide.

“The protection improved to 79% effectiveness for COVID-19 infection and 81% for COVID-19-related hospitalizations,” the Janssen-led research team wrote in a study posted online in a preprint. This protection against infection still lagged behind the Moderna vaccine (93%) and the Pfizer-BioNTech vaccine (88%), but was better than the single dose Janssen vaccine (71%) in U.S. adults without immunocompromising conditions. The study was conducted from March 11–August 15, 2021, and therefore included many exposures to the Delta variant virus.

The company’s ongoing Phase 2 trial of a two-dose regimen looked even better when giving two doses, 56 days apart as it provided 100% protection against severe Covid-19 and 94% protection against moderate to severe Covid-19 in the United States. Globally, the two-dose regimen provided 75% protection against moderate-to-severe Covid-19, the company said.(See Moderna’s vaccine is the most effective, but Pfizer and J&J also protect well, CDC-led study says).

Overall, the data suggested protection with any vaccine should be stronger if people get boosters later, Dr. Dan Barouch, head of Beth Israel Deaconess’ Center for Virology and Vaccine Research, said in a report to CNN. He argued that, “If you wait longer and have boost at six months or later then you likely will have better boost.” I think this is because neutralizing antibodies to the adenovirus vector in this vaccine (induced by the first shot) decline over time, allowing the vaccine to work better in the second shot.

Therefore, given that all other vaccines were given as a two-dose regimen and showed better protection, why was Janssen’s vaccine given as a single dose? In the early days of COVID-19 vaccination, a single dose, especially with a temperature stable vaccine, was thought to provide a logistical advantage over two dose vaccines. It is now clear that protection, especially from variants like Delta, is of utmost value and takes precedence over the convenience of a single dose.

Given this data, the Janssen vaccine should only be used as two doses, and everyone who got a single dose should get a booster.

Published by jbakerjrblog

Immunologist, former Army MD, former head of allergy and clinical immunology at University of Michigan, vaccine developer and opinionated guy.

3 thoughts on “Janssen’s “booster” vaccine.

  1. Oh Dr. Baker, can someone please coach the head of the CDC on public speaking? Today she said 15% of pregnant women are vaccinated and that puts them at high risk of covid.  Backwards messaging. No wonder many people are confused/suspicious. Thanks for all you do. – Linda Webb Sent from my T-Mobile 5G Device


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