This year’s flu shot delivers a bigger punch against the illness than last year’s vaccine, which likely was an ingredient in keeping a bad flu season from turning into a really bad season, the federal government says.
The vaccine for this year’s strain of influenza prevented about 55% of flu in children and 45% in adults, a major improvement over the effectiveness of the 2018-2019 injection, which was 29%, the U.S. Centers for Disease Control and Prevention reported this month.
The vaccine effectiveness report said a 45% effectiveness is “particularly important in the context of the substantial prevalence of influenza in the United States.”
The effectiveness study by CDC scientists looked at 4,112 people older than 6 months in Michigan, Pennsylvania, Texas, Washington, and Wisconsin between Oct. 23 to Jan. 25. The subjects were enrolled in the study if they had developed a cough in the previous week and had not been treated with antiviral drugs.
Some places in the country, including Ohio, had an unusually hard flu season. Most years, the A strain arrives first from Australia and peaks in mid-January, then the less-severe B strain comes in. This year, the B strain arrived first in Ohio, which triggered a longer flu season.
On Friday, the CDC said 105 children have died from flu this year, including two in Ohio. Other than 2009, when the world last experienced a flu pandemic, “this is the largest number (of child deaths) reported for this time of the season since reporting began for the 2004–05 influenza season,” the vaccine study said.
Although the flu season in Ohio has been bad, the state Department of Health reported Friday that for the first time in five weeks, hospitalizations for the flu have fallen, even as cases of the trailing A strain predominate. The number still is higher than the five-year seasonal average, but other seasonal measures of illness such as clinic visits fell across the board, Ohio officials said Friday.
The tougher flu season is a reason that Deer Park schools were closed this Thursday and Friday. Schools in Reading, Bracken County and Three Rivers were earlier this winter. A Northern Kentucky child was among the season’s first deaths caused by flu.
Developing seasonal flu vaccine is as much art as science. Over the summer, U.S. vaccine makers identify the strains circulating during the winter Down Under and base their product on what they anticipate will proliferate in the Northern Hemisphere.
Another key defense against flu and other viruses is hand-washing, for 20 seconds with warm water and soap. Keep the hands away from the mouth and nose. Stay home if you are sick.
The vaccine-effectiveness report, which the CDC released Feb. 21, said the arrival of the A strain came too late in its fact-gathering that researchers didn’t have enough patients to study. The researchers estimated this year’s vaccine has about the same effectiveness on the A strain as in previous years, about 30%.
The CDC and other public health agencies say even if a vaccine is less effective than hoped, a flu shot offers a measure of protection against predominant strains, especially for the elderly and for children. A shot, even late in the flu season, also can make a bout with flu milder.
The study’s authors said their findings were limited because of the small sampling of the A strain. Revised estimates expected later in the year will no doubt change the findings on effectiveness, not just on preventing outpatient visits but also hospitalizations.