According to new CDC data, the flu vaccine was only 16 per cent effective against the most common strain of the virus this past winter.
However, the case numbers have still remained unusually low so there is no need to worry.
That’s right, a new Centers for Disease Control and Prevention analysis found that the flu vaccine was a really bad match for the predominant influenza strain that circulated this winter.
Luckily, this also marked the second consecutive year with a really mild flu season thanks to all the COVID-19 precautions in place contributing to protecting people from catching the flu as well.
The results come from CDC’s surveillance program of people with flu-like symptoms who stop by outpatient sites all over the country and they show that the odds of catching the flu virus were only a little lower in the case of vaccinated people.
The annual anti-influenza vaccine was, therefore, determined to be only about 14 per cent effective against all strains of the virus as well as 16 per cent effective against the predominant strain this winter – the A(H3N2) viruses.
To make it clear, these numbers are really low compared to the 50 per cent threshold required for a vaccine to be categorized as helpful.
In fact, the percentages are not even high enough to be considered statistically significant.
The researchers who published the results in the CDC’s Morbidity and Mortality Weekly Report, explained that the vaccine “didn’t reduce the risk for outpatient respiratory illness caused by influenza A(H3N2) viruses that have predominated so far this season.”
In reality, even in a good year, flu vaccines are usually far from being perfect.
This is because the strains that infect people are in the process of constant evolution, which means that scientists are expected to attempt to predict what the strains will look like before each flu season begins in order to match them to the strains included in the shot.
Usually, the vaccine features 4 strains at a time.
It’s pretty much a guessing game which usually results in a flu vaccine 50 per cent to 60 per cent effective although sometimes the results are much more mismatched, such as in the past winter!
The H3N2, this year’s predominant strain, is also known for being harder to predict than other such subtypes of flu so that’s contributed a lot to the vaccine being so ineffective.
As mentioned before, however, there was no serious reason for concern regardless of this situation.
In reality, cases, hospitalizations and deaths have all been going down in numbers, reaching historic lows and this trend has been going on for the past two years, although it has to be mentioned that they were not as low in the winter of 2022 as during the 2020-2021 season.
In fact, the numbers were so low at the time that the CDC was not even able to estimate vaccine effectiveness!
But the few cases from the previous season most likely also contributed to making the predominant strains this year even harder for scientists to predict.
These past two flu seasons have been so meek mainly due to all the health measures taken to slow down the spread of the much more contagious and dangerous COVID-19 virus, such as wearing masks regularly and social distancing, just to name a couple of the effective measures imposed.
Just last month, the World Health Organization issued their recommendations on the flu shot for the upcoming Northern hemisphere winter and it included calling for more updates on the H3N2 strains as a reference.
However, the CDC authors noted that “predicting circulation of virus subtypes and predominant clades within subtypes remains challenging.”
All in all, despite the fact that this year the flu vaccine was practically useless, it is still very much worth getting.
After all, during any typical year, flu shots usually manage to prevent millions of cases, tens of thousands of hospitalizations as well as thousands of deaths even when taking into consideration that in the United States, only around half of the population gets vaccinated against the flu anyway.
More good news is that there are also next-gen vaccines in development that might just lead to a better match to the dominant strains of the virus.
In other words, a universal or longer lasting flu vaccine is right within our grasp!