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Are boosters needed for J&J vaccine?

Question: I have had several friends who got the J&J vaccine who are now asking if they should also get a dose or full Pfizer regimen. I’m not seeing anything from CDC on this yet and think it’s just concern about Delta that is fueling the questions. However, one friend in Texas had his physician recommend a follow-up Pfizer regimen. Is this an interpretation by one physician or can we expect this recommendation? My gut and research tells me it’s not needed, but figure I’d ask since others may have a similar question.

Answer: We talked about booster shots in our Q&A of 7/27, but didn’t get into the specifics of J&J.  As I wrote then, we still don’t know whether or when we’d need booster shots– and that applies for J&J too.  At least for now, public health authorities (like FDA) do not think it is necessary.  For example, Dr. Fauci recently told CNN, “given the data and the information we have, we do not need to give people a third shot, a boost, superimposed upon the two doses you get with the mRNA (Pfizer/BioNTech and Moderna vaccine) and the one dose you get with (Johnson & Johnson).”  That said, folks should talk with their doctor if they are concerned, and especially if they are immuno-compromised; evidence is increasing indicating that a booster dose could be beneficial for immuno-compromised individuals.  When it comes to J&J’s durability against the Delta variant, here’s a slice of what we currently know (you’ll see that some of it is conflicting!):

  • Efficacy of J&J is lower than mRNA vaccines. In clinical trials, J&J was found to have 66.9% efficacy against moderate to severe disease 2+ weeks after vaccination (95% CI: 59.0%-73.4%).  For comparison, Pfizer and Moderna’s efficacy was 95% and 94.1%, respectively.  Since J&J has lower efficacy at baseline, any reduction in effectiveness will have a more profound impact. 
  • Durability of J&J against Delta may be substantially reduced. A preprint posted on July 21, Comparison of Neutralizing Antibody Titers Elicited by mRNA and Adenoviral Vector Vaccine against SARS-CoV-2 Variants, presented results from a lab-based study that examined antibody responses to various variants of concern from blood serum drawn from individuals vaccinated with either J&J, Moderna, or Pfizer.  Researchers found that all three vaccines had reduced antibody response to variants of concern, including Delta, however, the reduction varied dramatically by vaccine type.  For Pfizer and Moderna, the reduction was unlikely to limit the durability of the vaccines.  For J&J, however, the reduction was bigger, raising the potential for decreased protection against Delta and other variants of concern.  This study has many limitations, including that it was lab-based, measuring only one element of immune response, and included serum samples from only 10 individuals vaccinated with J&J.  It’s data are important, but not strong enough to draw conclusions.  Additionally, the findings are in conflict with another set of recent findings…
  • Durability of J&J against Delta may persist. Two small lab-based studies by J&J scientists indicate that J&J durability against the Delta variant persists.  A letter printed on July 14 in New England Journal of Medicine, Durable Humoral and Cellular Immune Responses 8 Months after Ad26.COV2.S Vaccination, presented results from a lab-based study of immune response over an 8 month time-period among 10 individuals who were vaccinated with J&J (1 dose) and 10 individuals vaccinated with J&J (2 doses) and 5 individuals who received placebo.  Researchers found durable antibody response over the 8 months, even among those participants who received the 1 dose regimen, and even against the Delta variant.  And a preprint study posted on July 1, Ad26.COV2.S elicited neutralizing activity against Delta and other SARS-CoV-2 variants of concern, observed antibody response to Delta among blood serum drawn from 8 participants previously vaccinated with J&J.  
  • Real-world data are needed, but a recent glimpse is concerning. As you know, CDC published results from its outbreak investigation in Massachusetts.  There were 346 vaccinated individuals who experienced breakthrough infections (159 vaccinated with Pfizer, 131 with Moderna, and 56 with J&J).  Only 4 vaccinated individuals were hospitalized– 1 of whom had been vaccinated with Pfizer and 3 of whom had been vaccinated with J&J.  Simple math here (my own): 0.6% of Pfizer breakthrough cases resulted in hospitalization, 0% of Moderna breakthrough cases, and 5.4% of J&J breakthrough cases.  That’s a huge difference!  That said, this back of the envelope calculation is overly simplistic– we’d need bigger sample sizes and to control for other factors (like age and pre-existing conditions) to draw conclusions.  Stil… this glimpse is concerning.
  • Data on mixed dosing for AstraZeneca, another viral vector vaccine, is promising. Running out of time/space here, but wanted to note that J&J is a viral vector vaccine, like AstraZeneca.  Recent data on “mix and match” dosing with AstraZeneca indicates that immune outcomes may be enhanced by coupling one dose of the viral vector vaccine with a 2nd dose of mRNA vaccine.  These findings could have relevance for other viral vector vaccines, like J&J.