Immunological evaluation of influenza vaccine effectiveness against A/H1N1/pdm09 strains circulating in Iran

In 2015-2016 flu season, the subtype A/H1N1/pdm09 was reported with a widespread of 92% in Iran.  A phylogenetic study based on the HA protein located the viruses in the new subgroup 6B.1. Therefore, by observing this change, the effectiveness of the vaccine was investigated from an immunological point of view.

The investigated viruses were selected from among the sequenced samples based on the diversity and abundance of substitutions, by aligning with the Bioedit software and drawing a phylogenetic tree by the maximum likelihood method in the Mega software, and were propagated by MDCK cells. Next, by injecting two doses of human influenza vaccine two weeks apart into the two rabbits, their serum on day (0) before immunization, 21 and 30 days after the injection, isolated and after treatment, the antibody produced was used for Hemagglutination inhibition (HI) test. The data were analyzed in the Excel chart.  

The mean HI titer in the positive control sample was 960, and in samples 831, 836, 807 and 808 were 40, 20, 180 and 120, respectively. The results showed that the antibody obtained from the vaccine had neutralizing properties against the circulating viruses, but it was significantly reduced compared to the reference strain (P<0.001). No titer was observed in the negative control sample.

The requirement of genetic and immunological evaluation of vaccine efficiency for influenza viruses is necessary every year; so it is essential to provide appropriate methods available to laboratories.