COVID-19: Updates and Predictions for the Bivalent Booster

Paul G. Auwaerter, MD


July 27, 2022

This transcript has been edited for clarity.

Hello. I'm Paul Auwaerter with Medscape Infectious Diseases, speaking from Johns Hopkins University School of Medicine. I thought I'd focus on an important question that I have been asked by many colleagues, patients, family, and friends, which is, "Should I get a second booster now or wait?"

Much of this depends on understanding certain amounts of what's happening in the landscape of SARS-CoV-2 and recent FDA decisions. What's happening now, as many have heard, is that the current subvariants of Omicron have continued to quickly evolve such that BA.5 and BA.4 now are the most common subvariants being detected by genomic surveillance in the United States.

We also know from data from South Africa available in a preprint that these two variants, which were present in South Africa, had increased transmissibility with an R0 estimated at about 18, which is quite similar to measles — highly contagious. In fact, I came down with COVID-19 the same day as Tony Fauci. I've had a second booster.

Not only is it highly transmissible, but also it appears to be even more likely to evade preexisting immunity which, of course, is the hallmark of these variants as they continue to evolve. The good news is that there hasn't yet been a really striking increase in hospitalizations and deaths, but that's something that may not always be the case.

The second issue has to do with the recent VRBPAC meeting by the FDA — that's the Vaccine and Related Biological Products Advisory Committee meeting — held on June 28. They met to address a single question in their 8-hour meeting, which was, "Does the committee recommend including an Omicron component of the virus in COVID-19 boosters for the United States?"

There was quite a bit of data presented, but just some highlights that struck me were projections that there may be a novel variant emerging this fall where we might even have less protection from our existing vaccine such that the estimated deaths, if you look at a 1-year time frame from March 2022 to March 2023, could vary between 95,000 and 211,000. This is far more than might be seen with seasonal influenza, so it's a substantial problem.

We do know that the current vaccine, although it neutralizes BA.4 and BA.5, does so less effectively than BA.1. The other component that we're beginning to understand is that the effectiveness of the existing vaccine to prevent hospitalization seems to start significantly waning 9 months after last immunization.

The industry presented data on their clinical trials where they had developed vaccines based on the earlier Omicron BA.1. Moderna developed a bivalent vaccine with the ancestral component, which is our existing vaccine, along with BA.1, as did Pfizer. It looked like they provided neutralizing antibodies and it also had impact on BA.4 and BA.5.

Interestingly, Moderna has already been manufacturing this bivalent vaccine, but if there were a change to a BA.4/BA.5 vaccine, the earliest that these manufacturing facilities could pivot and produce this for a meaningful public administration would be October or November.

The VRBPAC voted 9 to 2 in favor of an Omicron component for the vaccine. There were two negative votes that mainly brought up that no one would know whether Omicron or any of its subvariants would be circulating in the BA.4 or BA.5 category, or any of the Omicron variants, later this year.

Two days later, Peter Marks, who heads up the vaccine division of the FDA, said that the FDA is going to update the booster with BA.4 and BA.5 as its component along with the existing, so we will have a bivalent booster. They do want clinical data but will not require it for this booster and will use instead BA.1-based data.

Again, it looks like it's only going to be later this fall that this new booster may be available. Interestingly, the WHO went with a BA.1-based vaccine, which they said is more distinct and offers a broader immune response.

What should we say about whether a patient should get a booster now or later? I would say that, to be up-to-date, which is the CDC parlance, getting all recommended boosters is the best strategy. That is now the bird at hand. We do know that a second booster was helpful in reducing serious illness in people over 60 years of age, and other data from Europe suggest the same.

If you want to wait for the bivalent vaccine, I think it poses the potential that you're going to be behind the variant changes that might be forthcoming in the fall, as BA.4 and BA.5 might be replaced because there are still billions of infections occurring regularly. We also don't have much in the way of clinical data, so that's what I'm encouraging for my patients.

I'm sure there will be different approaches here, but I do think that bird at hand is going to be better than waiting for the bivalent vaccine. Of course, if you get the second booster now, you'll likely be eligible by late fall or early winter for the bivalent booster as well.

Thanks so much for listening. I hope this was helpful. I wish you well. Continue to pay attention to the pandemic.

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