Influenza A (H3N2) Variant Virus


Low 2016/17 season vaccine efficacy against hospitalized influenza A(H3N2) among elderly: awareness warranted for 2017/18 season. 2017, Rondy, Euro Surveill

The effectiveness of the vaccine against A(H3N2) in the 2016/17 season among hospitalized elderly was 17%. Among those who were vaccinated also in the previous season, the effectiveness of the vaccine was -2% (negative). The authors expect, as in the next season it will not be particularly effective, since strain A(H3N2) in the vaccine of 2017/18 remained the same.


Contemporary H3N2 influenza viruses have a glycosylation site that is antibodies to antibodies elicited by egg-adapted vaccine strains. 2017, Zost, Proc Natl Acad Sci

This explains why the vaccine in 2016/17 was ineffective (because the virus is grown in eggs and mutates).


A Perfect Storm: Impact of Genomic Variation and Serial Vaccination on Low Influenza Vaccine Effectiveness During the 2014-2015 Season. 2016, Skowronski, Clin Infect Dis

In the 2014/15 season, the effectiveness of A(H3N2) vaccine in Canada was 53% for those who were vaccinated only this year, among those who were vaccinated also in the previous season, the efficacy was negative -32%. those who were vaccinated for 3 consecutive years, the effectiveness was -54%.
On average, the efficiency was -17%.


Impact of the repeated vaccination on vaccine effectiveness against influenza A(H3N2) and B during 8 seasons. 2014, McLean, Clin Infect Dis

The effectiveness of the vaccine against A(H3N2) in 2004-2013 was 65% for those who were vaccinated in the same season. Those who are vaccinated often have efficacy of 24%. Effectiveness from Type B influenza virus was 75% for those who have been vaccinated only this year, and 48% for those who are vaccinated frequently.


Effectiveness of trivalent inactivated influenza vaccine in influenza-related hospitalization in children: a case-control study. 2012, Joshi, Allergy Asthma Proc

The study for 8 seasons (1999-2007).The risk of hospitalization due to influenza in vaccinated children was 3.67 times higher than in the unvaccinated.
For these 8 years, strain A(H3N2) has not been guessed 5 times, and the strains A (H1N1) and B did not guess four times.

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