Fall bivalent boosters: Science update round 4

We got an early holiday present. One of the last puzzle pieces about the fall booster was released today: data on the effectiveness against severe disease. I also interviewed the CDC Program Lead for more context.

Science until now

We have ~9 lab studies and 1 real world study showing the fall boosters provide:

1. Greater protection against infection and transmission, by boosting our first line of defense—neutralizing antibodies. (See my previous updates here.)

2. Broader protection, or the ability to create antibodies that “see” more virus parts and “attach” more strongly compared to the antibodies we have right now. (See my previous updates on this here.); and,

3. Longer protection against infection and severe disease, even just by a few months. We are still at the mercy of time for this, but have promising data from the Beta bivalent vaccine clinical trials.

Until now, though, we didn’t know whether they provided additional protection against severe disease and hospitalization. We now have three real world analyses, and things are looking good.

Two new U.S. studies

Today, the CDC released studies answering the same question from two different perspectives.

The first study leveraged the IVY network—22 hospitals in 18 states. Scientists looked at hospitalizations from September 8 to November 30, 2022 among adults aged 65 years and older. This is what they found:

• Compared to no prior vaccination, effectiveness of the fall booster against hospitalization was 84%.

• Compared to 2+ previous mRNA vaccines, effectiveness was 73%.

The second study leveraged the VISION network—a network of nine hospitals in 11 different states. Scientists assessed emergency room and urgent care visits (a proxy for more severe disease) from September 13 to November 18, 2022. They included patients of all ages, not just over 65 years old. They found:

• Compared to no prior vaccination, effectiveness of the fall booster against emergency room or urgent care visits was 56%.

• Compared to 2+ previous mRNA vaccines, effectiveness was 31-50%.

  • This depended on timing of last dose. If someone got their last mRNA shot 2-4 months ago, for example, effectiveness was 31%. If the last dose was 12+ months ago, effectiveness was 50%.

U.K. analysis

This data comes on the heels of a report from the U.K. Health Security Agency that ran a similar analysis of their boosters. As a reminder, they used the BA.1 formula only for those over 50 years old, while the U.S. used a BA.5 formula for everyone. They found:

• Effectiveness against hospitalization was 57% compared to those without the Fall booster.

Broader context

I spoke with Dr. Ruth Link-Gelles a few days ago, as she is the Program Lead of COVID-19 Vaccine Effectiveness at the CDC and Lieutenant Commander in the U.S. Public Health Service. While she worked directly on these studies and probably could repeat the results like the back of her hand, I asked more about the context around these numbers. And, more importantly, how to talk Grandma into getting a vaccine today. Here is what she had to say:

Bottom line

The fall boosters work. There is now evidence fall boosters broaden protection, help against infection, protect against severe disease, and (we think and hope) provide longer protection. There is one major problem though: more than 150 million people are eligible for a fall booster in the U.S. and have yet to get one.

Love, YLE

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“Your Local Epidemiologist (YLE)” is written by Dr. Katelyn Jetelina, MPH PhD—an epidemiologist, data scientist, wife, and mom of two little girls. During the day she works at a nonpartisan health policy think tank and is a senior scientific consultant to a number of organizations, including the CDC. At night she writes this newsletter. Her main goal is to “translate” the ever-evolving public health science so that people will be well equipped to make evidence-based decisions. This newsletter is free thanks to the generous support of fellow YLE community members. To support this effort, subscribe below: