pfizer‘sand modernCompared to people who didn’t get the shot, the Omicron booster reduced the risk of mild disease from the XBB family of subvariants, according to a study from the Centers for Disease Control and Prevention published Wednesday.
The CDC study provides the first estimates of the real-world effectiveness of the Omicron shots against 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 antibodies that block infection.
For people aged 18 to 49, the Omicron booster reduced the risk of mild illness by about 48% two to three months after receiving the shot. According to the study, the shots provided 38% protection against mild disease for those aged 50 to 64 and 42% for those aged 65 and older.
CDC officials told reporters Wednesday that the study results are reassuring because people who received boosters had greater protection than those who received boosters. There should be more protection against critical illness, he said.
A CDC official and author of the study, Dr. “It roughly halves your risk of symptomatic infection at the population level,” said Ruth Link-Giles.
“What we know from past experience is generally that vaccines protect better against more severe disease,” Link-Gales 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 rising to dominance in the US and currently accounts for approximately 49% of new COVID cases nationwide. World Health Organization officials describe XBB.1.5 as the most transmissible variant of the virus to date, although there are no changes to suggest that it makes people sicker than other subvariants.
XBB.1.5 is very immunologically suppressive and has mutations that allow it to better bind to human cells. But the CDC study found that Omicron boosters provide as much protection against the XBB family as they do against the Ba.5 subvariant and its descendants, such as Bq.1 and Bq.1.1. Protection from mild disease from BA.5 family was approx.
“We did not see reduced vaccine protection against symptomatic disease for XBB and XBB.1.5 compared to other recent BA.5 variants,” said Dr. Brendan Jackson, head of the CDC’s COVID-19 response.
The study compared people who received the new booster with between two and four doses of the original vaccine. The boosters target Omicron BA.5 and the original strain of Covid that emerged in Wuhan, China, while the older shots only target the original virus strain.
People who only received the original shot usually received their last dose about 13 months ago. Link-Gels said they offered little protection from mild disease because of the lack of immunity seen with older vaccines. He said it is too early to draw conclusions about how protection from the Omicron boosters holds up over time.
“Even though you have reduced protection over time against symptomatic infection, you are still protected against more severe disease,” Link-Giles said.
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