Updated Covid-19 boosters that carry instructions to arm the body against currently circulating Omicron subvariants offer some protection against infections, according to the first study to look at how the boosters are performing in the real world. However, the protection is not as high as that provided by the original vaccine against earlier coronavirus variants, the researchers say.
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, called the new data “really quite good.”
“Please, for your own safety, for that of your family, get your updated Covid-19 shot as soon as you’re eligible to protect yourself, your family and your community,” Fauci said at a White House briefing Tuesday.
Uptake of the bivalent boosters, which protect against the BA.4/5 subvariants as well as the original virus strain, has been remarkably slow. Only 11% of eligible Americans have gotten them since they became available in early September.
The new study found that the updated boosters work about like the original boosters. They protect against symptomatic infection in the range of 40% to 60%, meaning that even when vaccine protection is its most potent, about a month after getting the shot, people may still be vulnerable to breakthrough infections.
That’s in about the same range as typical efficacy for flu vaccines. Over the past 10 years, CDC data shows, the effectiveness of the seasonal flu vaccines has ranged from a low of 19% to a high of around 52% against needing to see a doctor because of the flu. The effectiveness varies depending on how similar the strains in the vaccine are to the strains that end up making people sick.
The authors of the new study say people should realize that the Covid-19 vaccines are no longer more than 90% protective against symptomatic infections, as they were when they were first introduced in 2020.
“Unfortunately, the 90% to 100% protection was what we saw during like pre-Delta time. And so with Delta, we saw it drop into the 70% range, and then for Omicron, we saw it drop even lower, to the 50% range. And so I think what we’re seeing here is that the bivalent vaccine really brings you back to that sort of effectiveness that we would have seen immediately after past boosters, which is great. That’s where we want it to get,” said Dr. Ruth Link-Gelles, an epidemiologist at the US Centers for Disease Control and Prevention.