New Study Shows Annual Flu Vaccine Remains Effective in Children with Prior Vaccination

With the Northern Hemisphere’s 2018-2019 influenza season now officially here, health officials in the United States hope that the recent mild flu season in Australia and the Southern Hemisphere is a sign of what is to come in the United States this season.

The investigators on a new study published in JAMA Network Open studied the effect of prior influenza vaccination on influenza vaccine effectiveness (VE) in children. Some studies have found that prior vaccination may reduce current-season flu VE, particularly when similar flu strains are used 2 years in a row, though the study’s authors note that few studies have assessed this in children or examined the effect of flu vaccinations received in the prior 2 or 3 seasons.

The new study enrolled a total of 3369 children during the 2013-2014, 2014-2015, and 2015-2016 flu seasons. Of these children, 772 (23%) had a positive test result for influenza and 1674 (50%) were vaccinated in the enrollment season.

The investigators found that among LAIV recipients, VE against the H3N2 strain was much higher among children vaccinated in both the enrollment and 1 prior season than among those without the prior season vaccination. In addition, the VE of LAIV against the H1N1 strain was also higher among those with prior season vaccination than those in those without. Among children who had received the flu shot, VE for both influenza A strains was similar between children who had been vaccinated the previous year and those who had not.

Prior-season vaccination was not associated with reduced VE, according to the authors, concluding that their findings support current recommendations for annual influenza vaccination of children.

With the US Centers for Disease Control and Prevention (CDC) now including the nasal spray flu vaccine as one of the recommended forms of the annual vaccine, the American Academy of Pediatrics recently announced that it still recommends the flu shot over the spray for children. In an interview with Contagion®, study author Huong Q. McLean, PhD, MPH, noted that these changes in recommendations may be difficult for the public to track.

“The different messaging for flu mist may be confusing, but it is clear from both organizations that flu vaccination is recommended for all children 6 months and older,” Dr. McLean said. “Influenza is a serious illness. The severity of each flu season is unpredictable, and children die each year from the flu. Getting the flu vaccine every year is the best way to protect your child against the flu.”

The highly severe flu season of 2017-2018 was the worst the United States had seen in a decade and was marked by high rates of influenza-related hospitalizations and influenza activity that remained widespread for an extended period. The current flu surveillance report from the CDC indicates that the influenza activity in the United States. remains low at this time, with influenza A(H1N1)pdm09, influenza A(H3N2), and influenza B viruses co-circulating.

Vaccines strains for the 2018-2019 influenza vaccines include A/Michigan/45/2015 (H1N1)pdm09-like virus, an updated A/Singapore/INFIMH-16-0019/2016 A(H3N2)-like virus, and an updated B/Colorado/06/2017-like (Victoria lineage) virus. The quadrivalent vaccine also includes a B/Phuket/3073/2013-like (Yamagata lineage) virus. The nasal spray flu vaccine is recommended for use in nonpregnant individuals ages 2 through 49 years, after not being recommended during the previous 2 flu seasons.

In addition, on October 24, 2018, the US Food and Drug Administration approved Xofluza for the treatment of acute uncomplicated influenza in patients 12 older who have been symptomatic for no more than 48 hours.

“This is the first new antiviral flu treatment with a novel mechanism of action approved by the FDA in nearly 20 years,” FDA Commissioner Scott Gottlieb, MD, said in a statement. “With thousands of people getting the flu every year, and many people becoming seriously ill, having safe and effective treatment alternatives is critical. This novel drug provides an important, additional treatment option. While there are several FDA-approved antiviral drugs to treat flu, they’re not a substitute for yearly vaccination.”