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Previous vaccination with the seasonal flu vaccine does not reduce the effectiveness of the next season's vaccine in children aged 2 to 17 years. This is the conclusion of a study published today in JAMA network open.
"The results of the study reassure us that the vaccine is still a good thing to do every year," said Huong Q. McLean, PhD, MPH, lead author of the study and a research scientist. at the Marshfield Clinical Research Institute in Marshfield, Wisc., in an interview.
The previous season's coverage by the cover of the previous season's VE is under debate, with some studies showing that previous vaccination can reduce the EV of the current season. For example, a Canadian study published last year showed that if the influenza strains used in two vaccines are identical or very similar, the EV can be decreased in the second year.
Researchers have called this phenomenon the "antigenic distance hypothesis" (ADH) to describe the possibility that the effectiveness of the vaccine of the current season is hampered when the difference, or antigenic distance, between the two vaccines is small, but the difference between the vaccine strains and the current epidemic strain is great.
Numerous studies on DHA were conducted during the 2014-2015 influenza season, while the dominant subtype was H3N2 and influenza vaccines were underperforming in Canada and the United States. The H3N2 component of the vaccine that year was the same as that of the 2013-14 influenza vaccine, but it did not correspond to a new "derived" variant of H3N2 circulating in the population.
Focus on influenza vaccine and LAIV
"Most studies have been done on adults and have never really focused on children, and only on inactivated vaccines," McLean said. "Our study examined both inactivated influenza vaccine [IIV, or flu shot]and inactivated live attenuated vaccine [LAIV, or the nasal spray FluMist vaccine]. "
The current study was conducted in three influenza seasons (2013-2014, 2014-2015 and 2015-2016) in four US sites and recruited 3,369 children, 772 (23%) of whom tested positive. influenza and 1,674 (50%). %) were vaccinated during the recruitment season.
Among LAIV recipients, VE vs. H3N2 was significantly higher among children vaccinated both at school and in the previous season (50.3%, 95% confidence interval). [CI]17.0% to 70.2%) than in those who were not vaccinated during the previous season (-82.4%, 95% CI, -267.5% to 9.5%). EVD for influenza, the H1N1 strain was also higher in previously vaccinated individuals (47.5%, 95% CI, 11.4% to 68.9%) than in those who did not ( 7.8%, 95% CI, -101.9% to 57.9%)
).
Among the children who received the VII, however, the results were similar whether the child was vaccinated the previous year or not: 38.7% and 23.2% of VE, respectively, for H3N2 and 72.4% and 67.5% for H1N1.
"What was so interesting for us was that the association involved the type of vaccine used," said McLean. "The LAIV vaccine was more effective against H3N2 if a child had been vaccinated in a previous season, but the protection between seasons for H3N2 was the same as for the flu shot."
Unlike other studies, the protection provided by previous LAIV vaccination was particularly important during the 2014-2015 influenza season. McLean said that the same effect was not seen with H1N1.
"The antigenic distance hypothesis predicts a negative interference due to repeated vaccination when the vaccine strains are identical [vaccine strain 1 is the same as vaccine strain 2] and the viruses in circulation are adrift, as in the 2014-2015 season. However, the antigenic distance hypothesis was based on simulations of serological response to inactivated vaccines, and differences in the adaptive immune response to LAIV and VII could result in different effects of repeated vaccination in children, "concluded l & # 39; study.
In a commentary on the study, Sarah Cobey, PhD of the University of Chicago, said the findings of the study "suggest additional support for the current recommendation of the Advisory Committee on Practices in immunization that children need to be vaccinated against influenza every year.) To enhance protection against influenza B, regular vaccinations could improve the performance of the components of influenza A (H3N2) and influenza A ( H1N1) pdm09. "
See also:
October 26 JAMA Network open now study
October 26 JAMA Network open now comment
February 10, 2017, CIDRAP News story "Studies highlight the effects of influenza vaccines in series, the benefit of the current vaccine"
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