This winter’s flu vaccine was a particularly bad match for the most common influenza strain in circulation, a new analysis from the Centers for Disease Control and Prevention found. Thankfully, the flu season was much milder than usual for the second year in a row, as ongoing covid-19 precautions likely blunted the spread of flu as well.
The estimates come from the CDC’s long-running surveillance program of people with suspected flu-like symptoms who visit various outpatient sites throughout the country. Overall, the odds of catching a case of confirmed flu were only slightly lower for vaccinated people, the researchers found. Against all flu strains detected at these sites, the vaccine was deemed to be 14% effective, as well as 16% effective at preventing cases of flu from A(H3N2) viruses, the predominant strain this winter. Numbers this low are far below the 50% threshold for a vaccine to be considered relatively useful, and they’re not even high enough to reach statistical significance.
In the words of the researchers, who published their results in the CDC’s Morbidity and Mortality Weekly Report, the vaccine “did not reduce the risk for outpatient respiratory illness caused by influenza A(H3N2) viruses that have predominated so far this season.”
Flu vaccines, even in a good year, are far from perfect. The strains of influenza virus that infect humans are constantly evolving, meaning that scientists have to try to predict what these strains will look like during the next flu season so that they can match them to the strains included in the vaccine (the vaccine will usually include four strains at a time). This guessing game often results in a vaccine that’s around 50% to 60% effective, but sometimes, as is the case this year, the mismatch can get worse. It doesn’t help that this year’s main flu is H3N2, a subtype of flu already known for being harder to predict than others.
gizmodo.com
The estimates come from the CDC’s long-running surveillance program of people with suspected flu-like symptoms who visit various outpatient sites throughout the country. Overall, the odds of catching a case of confirmed flu were only slightly lower for vaccinated people, the researchers found. Against all flu strains detected at these sites, the vaccine was deemed to be 14% effective, as well as 16% effective at preventing cases of flu from A(H3N2) viruses, the predominant strain this winter. Numbers this low are far below the 50% threshold for a vaccine to be considered relatively useful, and they’re not even high enough to reach statistical significance.
In the words of the researchers, who published their results in the CDC’s Morbidity and Mortality Weekly Report, the vaccine “did not reduce the risk for outpatient respiratory illness caused by influenza A(H3N2) viruses that have predominated so far this season.”
Flu vaccines, even in a good year, are far from perfect. The strains of influenza virus that infect humans are constantly evolving, meaning that scientists have to try to predict what these strains will look like during the next flu season so that they can match them to the strains included in the vaccine (the vaccine will usually include four strains at a time). This guessing game often results in a vaccine that’s around 50% to 60% effective, but sometimes, as is the case this year, the mismatch can get worse. It doesn’t help that this year’s main flu is H3N2, a subtype of flu already known for being harder to predict than others.
This Year's Flu Vaccine Was Basically Worthless
CDC data shows the vaccine was only 16% effective against the predominant strain this winter. Luckily, flu cases remained far lower than usual.
gizmodo.com
