The effect of COVID-19 variants on childhood vaccines

William J. Muller, MD, PhD: It’s worth talking about variants, because that’s kind of the discussion at the FDA review board meeting [Food and Drug Administration]. It has 2 components. First, do we expect this to be a 3-dose vaccine for everyone in the future? I think the clearance will be for a 2-dose vaccine from Moderna and 3 doses from Pfizer. But everyone is waiting for a possible third dose of Moderna. They intentionally use the term third dose ’cause we throw around the term booster doses if there is no need for a third dose. Do you have any thoughts on this, and do you think we need to make this better understood by parents and the public?

Paul A Offit, MD: This is a 3 dose vaccine. Moderna will launch a 2-dose vaccine for children under 5 years old. It will probably be available as early as next week, and today is June 16. By June 20 or 21, it could be available for children under 5 years old. It was launched as a 2-dose vaccine, but the point that several committee members have made over the past 2 days is not to think of it as a 2-dose vaccine. 2 doses with the third dose as a booster. It would have to be a 3-dose primary vaccine if we are to get the kind of protection we need against these subvariants. In other words, the primary series is 3 doses, and increase is the wrong word. Because the way the CDC [Centers for Disease Control and Prevention] defines this is that you are fully immunized with 2 doses, but up to date with a third dose. It’s wrong. This is a 3-dose primary vaccination for your children. Pfizer’s vaccine for children under 5 is currently a 3-dose vaccine, but I know Moderna is doing studies with 3 doses, and they should have those studies available, they say, by July. So I think we will have this third dose very soon, which would be given months after the second dose.

William J. Muller, MD, PhD: The next question that many people have is whether the third doses that may be given in the coming months would be specifically for the variants. Moderna had data last week in adults that suggests, at least in antibody studies, that the neutralizing ability of people who received a variant vaccine was better than if they had received an additional dose of the vaccine based on the original strain of the virus.

Paul A Offit, MD: This is an important point. On June 28, the Vaccine Advisory Committee will meet to discuss this question: Should you administer a very specific vaccine in the fall? The so-called bivalent vaccine, where one of the mRNA components is against the ancestral strain, and the other is for Omicron. There’s plenty of evidence why that wouldn’t be a value. I know that’s a contrary view, but here’s what I would say. The good news about the ancestral vaccine is that a third dose clearly increases your antibodies against the Omicron subvariant, as Pfizer showed in data presented yesterday for the child under 5. With 2 doses, they had no neutralizing antibodies against Omicron. With this third dose, they did, and that’s the good news of this ancestral vaccine. If you give 2 doses of the ancestral vaccine and a third dose with the ancestral versus 2 doses of the ancestral vaccine and a third dose with the Omicron vaccine, is it better to have Omicron as a third dose in an HIV-positive person? Because a large percentage of this country is HIV positive. So if you only look at people who are HIV-negative, you’re talking about a very small percentage of people in this country who have already been naturally infected, immune, or both. You’re probably talking about at least 80% to 90% for people who are already HIV positive. And when you look at that data in the person who is HIV-positive, there’s not much difference. Also, in non-human primate studies, when they give 3 doses of the ancestral vaccine or 2 doses of the ancestral vaccine and then the Omicron booster… there is no difference. Unless there is data to the contrary to this data, I don’t see the point of making the vaccine specific to Omicron. I may be in the minority here. But if we want to follow the science, we have to make it clear that the science proves it.

William J. Muller, MD, PhD: I don’t disagree with you. I was going in this direction because one of the questions a lot of providers are going to get from parents who are about to start vaccinating their children is, “Do I have to wait until the fall and get the first set of a variant vaccine? “And from what you’re saying and from what I understand from the data, it makes more sense to get vaccinated sooner than to wait for a specific vaccine, because your protection is likely to be similar, at least against severe disease, which is the goal whether or not you get antibody levels that are significantly higher in neutralizing capacity. And an in vitro study doesn’t necessarily tell you if you’re protected against the disease, and the 2 are correlated to some extent. But if I have 5 times the level I need for disease protection versus twice the level I need for disease protection, maybe it doesn’t matter. I want to get twice the level sooner.

Paul A. Offit, MD: That’s absolutely correct. If you look at people with HIV who get the Omicron booster or the ancestral strain booster, the Omicron is about 1.7 times higher, which, while statistically significant, is unlikely to be clinically significant and will be without no doubt short-lived. It is probably not associated with an increase in memory B or T cells. If this is the best data to show, it is difficult to adopt a more expensive strategy.

William J. Muller, MD, PhD: I think this is an important point for the providers listening to us to understand.

Transcript edited for clarity

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