Influenza vaccine un- neutralized viruses associated with a specific seasonality pattern in Uganda: the HA/ HAI approach

BackgroundSeasonal Influenza vaccination is important in combatting influenza virus infections and severe disease associated with the infection. Hemagglutination (HA) and Hemagglutination Inhibition (HAI) assay has been used... [ view full abstract ]

Background

Seasonal Influenza vaccination is important in combatting influenza virus infections and severe disease associated with the infection. Hemagglutination (HA) and Hemagglutination Inhibition (HAI) assay has been used over the years to access the influenza vaccine’s effectiveness to neutralize the circulating influenza virus strains. In this research, we analyzed the seasonality and severity of influenza viruses which were not neutralized by the World Health Organization (WHO) recommended vaccine but showed hemagglutination (HA) on red blood cells, from 2012 to 2015.

Method

Clinical ILI and SARI samples positive for Influenza viruses by Polymerase Chain Reaction (PCR) were inoculated and propagated on Madin-Darby Canine Kidney (MDCK) cell line. Hemmaglutination and Hemmaglutination inhibition (HA/HAI) test was carried out using guinea pig erythrocytes. All viruses that showed HA titre but were not neutralized on HAI by the WHO recommended influenza vaccine for that year were recorded in MS- excel. Epidemiological data (seasonality and severity) corresponding to the viruses as captured on Influenza investigation forms were analyzed.

Results

A total of 17 influenza A viruses were not neutralized on HAI by the recommended WHO influenza vaccine for the year 2012 and 2015. AH3N2 viruses showed no neutralization at 65% compared to 35% by AH1N1 2009 pandemic strains.

The seasonality circulation of the non – neutralized AH3N2 viruses corresponded to the late rainy season in Uganda from October to January for both 2012 and 2015, while AH1N1 2009 pandemic influenza viruses corresponded to the annual dry season in Uganda between June and July 2015 with only one virus detected in January 2013. The severity of the infection was none the less similar to seasonal influenza viruses and the patients had no underlying medical condition (Asthmatic, Heart problems or TB).

Conclusion

Seasonal influenza A virus strains which cannot be neutralized by the recommended WHO vaccines have been demonstrated to circulate at points in time. We recommend sequencing of these strains to ascertain genetic differences between neutralized and non- neutralized strains.