During the current influenza season, to date seven variant influenza cases associated with hogs have been diagnosed involving four infected with H1N2v, two with H3N2v and one of H1N1v.  In all cases, there was no evidence of human-to-human transmission and the cases were regarded as sporadic.  Investigation confirmed contact with hogs either at livestock shows or from occupational exposure.  The two most recent cases occurred in Ohio and Pennsylvania.

In a commentary in ProMED, the moderator noted that high dose influenza vaccines offered enhanced protection for those over 65 years of age.  Depending on homology with the infective strain, both symptoms and hospitalizations should be reduced.  This was confirmed, in part, by a Kaiser Permanente study in southern California comparing the effectiveness of a high-dose adjuvant product , recombinant and standard dose cell-derived vaccines in comparison to conventional egg-derived products.  Among the combinations, standard dose cell-derived vaccines showed superior protection compared to standard-dose egg-based vaccines as measured by comparative vaccine effectiveness based on visits to physicians and hospitalizations.

Dr. Jennifer Ku, an epidemiologist with Kaiser Permanente, noted, “While seasonal variation exists, it is expected that seniors will continue to benefit from flu vaccines with higher levels of antigen.

Determining the most effective vaccination programs and vaccines for various demographics in the U.S. is very much a work in progress.  At the very least, all who come into contact with live poultry should receive the seasonal vaccine and if over 65 years of age, an available product with high antigen content.

The new range of cell-based vaccines and possibly in the future, mRNA products, will offer higher levels of protection compared to traditional egg-derived vaccines. Antigens in these products are selected six months in advance of the influenza season and frequently, field strains of influenza differ from the selection incorporated in the vaccine reducing the level of protection for recipient populations.

It is estimated that between 2014 and 2022, vaccine effectiveness has remained at a low level of approximately 50 percent mainly due to evident mismatch between vaccine and circulating strains. The CDC estimates an average annual mortality of 35,000 from influenza and its complications. For the 2024 influenza season the U.S. will experience 28 million cases with 310,000 hospitalizations at immense cost to the economy. Preventive vaccination albeit of varying effectiveness would reduce clinical cases and the cost of health care borne by the entire population.