Pfizer‘s 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 18 to 49 years of age, the omicron booster dose reduced the risk of mild disease from XBB subvariants by approximately 48% two to three months after receiving the vaccine. According to the study, vaccinations provided 38% protection against minor illnesses in people aged 50 to 64 and 42% in 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. Protection against serious diseases should be higher, although that data is not yet available, they 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, on the 18- to 49-year-old age group.
“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.
Scientists have found that XBB.1.5 is highly immune avoidable and has mutations that allow it to better attach to human cells. But the CDC study shows that the Omicron boosters offer about as much protection against the XBB family as they do against BA.5 and its descendants such as BQ.1 and BQ.1.1.
For example, adults aged 18-49 who received the omicron booster had a 52% reduced risk of mild disease from BA.5 and its offspring compared to a 48% reduced risk for the XBB family.
“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.
The CDC study looked at the Covid test results of about 29,000 people from December to January 13. During this period, XBB.1.5 increased from 2.4% of cases to around 37%. Among the more than 13,000 people who tested positive, 78% caught a BA.5-related subvariant and 22% caught an XBB-related subvariant.
The study did not perform detailed genomic analysis on every positive test sample to determine with 100% certainty which subvariant caused the infection. Instead, the scientists used a curd in PCR tests to determine which variant was likely to have caused the infection.
Subvariants related to BA.5 have a mutation that deletes a gene on the viral spike that tests target, while XBB subvariants lack this deletion. If the gene is detected it is likely XBB and if not detected it is likely related to BA.5.
https://www.cnbc.com/2023/01/25/covid-omicron-boosters-offer-some-protection-against-xbb-variant.html Covid Omicron boosters offer some protection against the XBB variant