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Does the flu shot lose effectiveness if you receive it every year?



There's more evidence than ever that it's a good idea to do your flu shot – and every year. Some studies had previously suggested that repeated vaccinations could affect the effectiveness of the shot year after year, although most findings were inconsistent and inconclusive. Now, a recent and more extensive study found no evidence for such an effect. In fact, according to the researchers, the annual vaccine seems to increase immunity in some cases.

The new study, published last week in JAMA involved more than 3,000 children aged 2 to 1

7 years visiting the doctor for an acute respiratory disease between 2013 and 2016. All visits were during the flu season, but only 23% of the patients were positive for the flu.

When they looked at the patients' vaccination records, the patients researchers found out that for children who had been vaccinated during the current flu season, as well as for the previous one, no influenza was diagnosed than for those who only during the been vaccinated this season.

LINK: Why You Should Get the Flu Shot Every Year

The effects varied according to type of influenza (influenza A or B), type of vaccine (nasal spray versus flu shot), and year. Overall, however, there was no scenario in which vaccination for two years in a row was associated with less efficacy than vaccination only in the current season.

"In other words, there was no evidence of decreased efficacy of vaccines for common vaccines. The study included seasons in which such effects were reported elsewhere," wrote Sarah Cobey, Associate Professor of Ecology and Evolution at the University of Chicago, in a related comment. The study is an "important step forward" to better understand the efficacy of flu vaccines, Cobey wrote.

In some cases, the flu vaccine seemed to actually increase protection each year. For example, children who received the FluMist Nasal Spray during the current season were less likely to receive the H3N2 strain of influenza (the most dangerous type that was in circulation last year) if they had been vaccinated the year before. Link: 25 Survival Routes to Cold and Flu

And with influenza B – one of two common types of flu that circulate seasonally in the US – a previous year's vaccine seemed to provide some immunity, even for children who have not been re-vaccinated in the current season.

The researchers found similar results for additional analyzes, including vaccinations in two and three previous seasons.

Since the study was conducted in children, it is not clear whether the same patterns would apply to adults. (A study published in the Canadian Medical Association Journal earlier this year, however, found that repeated vaccinations protect people over the age of 65.) And because every flu season is different – and the vaccine every year different values ​​has efficacy – the authors of the study say there is still much to learn.

RELATED: The 10 Biggest Myths About the Influenza

"To better understand the effect of a repeat vaccine on the efficacy of vaccines, if any For each type of vaccine, additional studies in different populations are available for each type of vaccine required, "says Dr. Huong McLean, researcher at the Marshfield Clinic Health System and first author of the study, Health .

] But for the time being, she says, the results are reassuring – especially for parents wondering if their children should be vaccinated every year. "The flu shot every year is still the best way to protect against the flu," says McLean.

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