Are the updated COVID vaccines preventing severe disease?

Yes. The updated COVID vaccines are showing strong protection against severe disease in the real-world.

Several new studies have estimated the effectiveness of the updated (XBB.1.5- targeted) COVID vaccines that rolled out this past fall. In the Netherlands, researchers linked data on hospital admissions to vaccine registry data for people who were at least 60.

Their fall vaccine campaign began in early October, and hospitalization and ICU admissions were evaluated through early December. People who got the updated shot had roughly 70% fewer COVID hospitalizations and ICU admissions over the next two months compared to people who did not get the updated shot (but who had previous COVID shots). This measure is called “effectiveness.” A similar analysis in Denmark found a 76.1% reduced risk of COVID-19 hospitalization for those who got the updated vaccine.

New data from the US look very similar. In the Kaiser Permanente Southern California health system, people (aged 18+) who received the updated XBB.1.5 vaccine had:

·      63% lower odds of COVID-19 hospitalization

·      58% lower odds of an emergency room or urgent care visit

·      58% lower odds of an outpatient visit

The updated vaccine reduces the risk of severe outcomes. This is true when we compare risks between those who got the updated vaccine and those who were never vaccinated. But getting the latest updated shot also reduced the risks compared to those who had received all previous COVID-19 vaccines but *not* the updated version. This highlights the importance of getting the updated shot even if you had all your previous doses.

Real-world data have limitations, including the fact that people who choose to get their updated shot may be systematically different from those who don’t. In theory, this can work both ways. More vulnerable people may get their shot first but also have a higher risk of ending up in the hospital, making the vaccine look less protective than it really is. Alternatively, people who are especially health conscious may be more likely to get their shot and stay healthy for other reasons, making the vaccine look more protective than it is. These studies all took various statistical steps to account for these differences, which we found reasonable (though never perfect!).

Another caveat is the short follow-up time of these studies—these estimates are all within the first two months after vaccination, so we don’t know how long this kind of protection will last—but hopefully, those data will be coming in due time.

Combined with previous lab data showing the updated vaccines elicit a good antibody response even against new variants like JN.1, these new data strongly suggest the updated vaccine is well worth getting.

Stay safe, stay well.

Love,

Those Nerdy Girls