17 November 2021 Blog Post: Mix and Match

With three options for initial adult vaccinations (J&J, Pfizer and Moderna) and three choices for boosters (J&J, Pfizer and Moderna), is there a ‘best’ option of vaccine + booster? Do you stick with the same or consider a ‘mix and match’ scenario?

Unsurprisingly (for those of you that have been following the pandemic), there are very little data available to help make this decision. The only head to head study comes from the NIH (link: https://www.medrxiv.org/content/10.1101/2021.10.10.21264827v2.full), in which 458 volunteers who had been fully immunized with either Pfizer’s, Moderna’s or J&J’s shot were given a booster four to six months after completing their initial vaccine regimen. They were divided into groups based on the vaccine they first received, then given either a matching booster from the same developer or a shot from one of the other two. Each group has only about 50 observations (range: 48-51). The table below summarizes the observed increase in antibody binding Units/ml with the Day #1 to Day #15 increases associated with each mix/match scenario. 

The paper does include antibody levels up to Day #29 for all groups except for those receiving the Pfizer booster. So to present as complete as data as possible, results from Day #15 are summarized here:

So what do we see from these data?

  1. In all cases, the additional dose increased antibody levels against the coronavirus, a change that’s generally associated with greater protection from COVID-19.
  2. At  baseline (month 4-6 from primary vaccine series completion), J&J has significantly lower antibody levels than the mRNA vaccines (Pfizer/Moderna). 
  3. Moderna had the highest antibody levels at baseline among all 3 vaccine groups
  4. Moderna also appeared to provide the biggest ‘boost’ among all 3 vaccine groups
  5. Boosting an initial J&J vaccination with either of the mRNA vaccines appeared to provide a much higher (nearly 10-fold) neutralizing antibody level (2549, Pfizer; 3203, Moderna) than did a second J&J (326)

But here is the biggest limitation:  the Moderna dose used in the study was the 100 microgram dose currently authorized, rather than the 50 microgram dose the company has requested and was subsequently FDA approved as a booster shot. (The New York Times commented that ‘it seems unlikely there will be much of a difference” – link: https://www.nytimes.com/2021/10/27/well/live/covid-booster-shot-mix-and-match.html).  

However, with the recommendation for everybody in the State of California over the age of 18 to now receive a booster, it would have been helpful to have more robust data to support matching or mixing.

𝗦𝗶𝗴𝗻 𝗨𝗽 𝗳𝗼𝗿 𝗢𝘂𝗿 𝗡𝗲𝘄𝘀𝗹𝗲𝘁𝘁𝗲𝗿

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