Mixed Vaccine Boosters: A Complex and Uncharted Territory for COVID-19 Prevention

Virologist Angela Rasmussen's recent decision to receive a Pfizer-BioNTech coronavirus vaccine booster shot, despite already having received a Johnson & Johnson vaccine, has sparked a debate among experts and raised questions about the need for combined vaccine boosters. Rasmussen's concerns about the emergence of the delta variant and the potential for vaccine-resistant strains have led her to seek additional protection. However, her actions are not without controversy, as the combination of the two vaccines has not been recommended by any U.S. health agency, and the safety and efficacy of such a combination are still unclear.

Key Takeaways:

• The effectiveness of the Johnson & Johnson vaccine against the delta variant and other variants has not been extensively studied, leading to concerns about the need for boosters.
• The Pfizer-BioNTech and Moderna vaccines, which belong to the mRNA class, have shown robust protection against the delta variant and other variants, but the duration of that protection is still unclear.
• A small study found that a single J&J shot produced neutralizing antibodies against delta and other common variants, but the overall amounts of those antibodies declined only slightly in eight months.
• The National Institutes of Health (NIH) has announced a clinical trial to evaluate the safety and immune responses to a mixed booster regimen, but results are not expected until later this summer or early fall.
• Experts have cautioned against attempts to find boosters unless supporting data or an official recommendation emerge, and warned that getting a booster in the absence of data supporting its necessity is not safe.
• The interval between becoming fully vaccinated and needing a booster hasn't been determined, and the timing of boosters is still unclear.
• The FDA has stated that there are no data available on the interchangeability of the Johnson & Johnson vaccine with other COVID-19 vaccines, and that they would need to review any new data regarding the use of a different vaccine booster.
• Experts have urged people who are worried to consider adopting additional prevention strategies, such as wearing a mask if there are high rates of transmission in their community.

Statistics:

• By mid-June, 130 million Moderna and 175 million Pfizer shots had been administered to people in the United States, according to the Centers for Disease Control and Prevention.
• The Johnson & Johnson vaccine has administered 12 million doses in the United States, mostly to individuals who have not received mRNA-based vaccines.
• A small study released Thursday by Johnson & Johnson found that 10 people who had one J&J dose showed persistent immune responses against delta and other variants over eight months.

Sources:

• The Washington Post, citing "Two weeks ago"
• Robert Atmar, Baylor College of Medicine, "If you look at people who are being hospitalized now, it's really been those persons who have not been previously vaccinated"
• Dan H. Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center in Boston, "While it's likely that adding a booster to any of the available vaccines will increase immune responses, how that translates into clinical protection, that's the part that's not yet known"
• Rochelle Walensky, CDC director, "We have no information to suggest that you need a second shot after J&J even with the delta variant"
• FDA statement, citing "There are no data available on the interchangeability of the [Johnson & Johnson] vaccine with other COVID-19 vaccines"
• AstraZeneca press release, citing "Com-CoV clinical trial"
• Johnson & Johnson press release, citing small study on J&J vaccine effectiveness