After a lawsuit from public health organizations, a federal court blocked it, leaving the previous recommendation in place. But the case is ongoing, and earlier this year President Donald Trump issued an executive order directing the government to treat a recent HHS assessment as a “guiding resource” and to revisit the childhood vaccine schedule. That assessment argues that recent evidence behind annual flu shots for children, much of it from observational studies rather than randomized trials, is thin. While we believe that the evidence base, which in fact includes many clinical trials, is stronger than suggested by that assessment, it is correct to note that observational studies of annual flu shots suffer from various statistical biases.
Randomized trials have earned their reputation as the “gold standard” because they address a real statistical problem. When we simply compare children who got the flu shot with those who didn’t, for example, the two groups can differ in ways that have nothing to do with the vaccine, like how cautious their parents are or how often they visit a doctor. A randomized trial solves this by assigning the shot purely by chance, so the only way the groups differ is in whether they got a flu shot.
Young children tend to have their annual checkup around their birthday, and that visit is a convenient moment for a flu shot if the vaccine happens to be available in the pediatrician’s office. Children with fall birthdays, who tend to see their pediatrician in the fall, just as the season’s vaccine arrives, can get it then and there. Children with summer birthdays have to make a separate trip, which many families never get around to doing. And birth month is essentially random when it comes to the flu; there is no biological reason a child born in October should need a flu shot more than a child born in June.
For this new study, we took advantage of this same randomization, but this time we used it to estimate how effective the vaccine was in each of five recent flu seasons, tracking vaccination and influenza rates among two- to five-year-olds with fall vs. summer birthdays.
In every season we examined, the vaccine clearly worked as intended: for every 100 children vaccinated because of the timing of their birthday—the children whose shot hinged on that convenient scheduling—there were between 9 and 14 fewer diagnosed cases of influenza, depending on the season.
As helpful as accidental randomization can be, producing what are called “natural experiments” like this one, true randomized controlled trials remain the most rigorous form of evidence. But it is simply not feasible to run a trial to settle every question medicine and public health face each year. Trials are slow, expensive, and logistically challenging. And when it comes to research on existing treatments, they can be unethical, since researchers cannot withhold treatments believed to be effective just to keep proving the point.
With a bit of creativity and rigorous statistical methods, that evidence can be drawn from the data we already have in the form of natural experiments. The efficacy of flu shots in children is just one of thousands of questions we could answer this way—no new trial required.
Hence then, the article about clinical trials aren t the only way to know if flu shots work was published today ( ) and is available on Time ( Middle East ) The editorial team at PressBee has edited and verified it, and it may have been modified, fully republished, or quoted. You can read and follow the updates of this news or article from its original source.
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