Pfizeris and ModernAccording to a Centers for Disease Control and Prevention study released Wednesday, omicron’s Omicron boosters reduced the risk of mild disease of the XBB subvariants compared to people who didn’t receive the vaccine.
The CDC study provides the first estimate of the real-world effectiveness of the Omicron shots versus the XBB family of subvariants. Some scientists have warned that the XBB subvariants could cause another Covid wave because they are so good at evading the antibodies that block infection.
In people aged 18 to 49, the omicron booster reduced the risk of mild illness by about 48% two to three months after receiving the vaccine. According to the study, the vaccines provided 38% protection against minor illnesses for people aged 50 to 64 and 42% protection for people aged 65 and over.
CDC officials, speaking to reporters Wednesday, said the study results were reassuring because people who received the booster shot had more protection than those who didn’t. The protection against serious illnesses should be higher, it said.
“It reduces the risk of symptomatic infection by about half at the population level,” said Dr. Ruth Link-Gelles, a CDC official and author of the study.
“In general, what we know from the past is that the vaccines protect better against more serious diseases,” Link-Gelles said. “So these are estimates for symptomatic infections, and we would expect similar estimates for hospitalizations and deaths to be higher.”
The XBB.1.5 subvariant is rapidly gaining dominance in the US and currently accounts for about 49% of new Covid cases nationwide. World Health Organization officials have described XBB.1.5 as the most transmissible version of the virus to date, although it has no mutations that would suggest it makes people sicker than other subvariants.
XBB.1.5 is highly immune avoidable and has mutations that allow it to better attach to human cells. However, the CDC study found that the Omicron boosters provided about as much protection against the XBB family as they did against the BA.5 subvariant and its descendants such as BQ.1 and BQ.1.1. Protection from mild diseases of the BA.5 family was approximately
“We did not find reduced immunization protection against symptomatic diseases in XBB and XBB.1.5 compared to these other newer BA.5 variants,” said Dr. Brendan Jackson, head of the CDC’s Covid-19 response.
The study compared people who received the new booster vaccine to people who received between two and four doses of the original vaccine. The boosters target Omicron BA.5 and the original Covid strain that emerged in Wuhan, China, while the old shots only target the original virus strain.
People who received only the original syringes generally received their last dose about 13 months ago. They had very little protection from mild illnesses because of the drop in immunity seen with the old vaccines, Link-Gelles said. It’s too early to draw any conclusions about how the protection provided by the Omicron boosters lasts over time, she said.
“Even if you have diminished protection against symptomatic infections over time, you’re likely still protected against more serious diseases for a longer period of time,” Link-Gelles said.
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