The World Health Organization (WHO) has called for updates to flu vaccine formulations ahead of the upcoming influenza season, specifically to incorporate strains targeting H3N2. This strain has been responsible for a notable increase in seasonal influenza cases in various countries, including India, over recent months. H3N2, often categorized as a “superflu,” is acknowledged for its ability to cause a more severe form of influenza.

Influenza viruses undergo continuous evolutionary changes, making it necessary to reevaluate and modify vaccine compositions regularly. Even minor genetic shifts can compromise the effectiveness of immunity acquired through either previous infections or vaccinations. The WHO has urged manufacturers to focus on developing vaccines that address two strains of influenza A—H1N1 and H3N2 (Subclade K)—as well as a strain of influenza B virus using egg-based, cell culture-based, recombinant protein, or nucleic acid-based technologies.

Understanding H3N2 and Its Impact

Dr. Seema Dhir, an internal medicine expert affiliated with Artemis Hospitals in Gurugram, described H3N2 as a variant of the influenza A virus that is associated with more severe health issues compared to other flu strains. Initially identified in 1968, H3N2 was responsible for the Hong Kong flu pandemic, which lasted until 1970 and claimed an estimated one to four million lives worldwide. Currently, individuals infected with H3N2 commonly experience high-grade fevers and persistent coughs, with increased risk of complications, especially in the elderly and children, which can lead to greater rates of hospitalization.

Dr. Neha Mishra, a specialist in infectious diseases at Manipal Hospital in Bengaluru, emphasized that while the majority of influenza cases resolve without severe medical intervention, vulnerable populations such as older adults and immunocompromised individuals are at a greater risk for serious complications. She highlighted that early detection and effective management in these at-risk groups can enhance patient outcomes.

Annual Impact of Seasonal Influenza

The WHO estimates around one billion cases of seasonal influenza occur globally each year, which includes 3 to 5 million cases classified as severe illnesses. These infections contribute to approximately 290,000 to 650,000 respiratory deaths each annum. Alarmingly, 99 percent of fatalities related to influenza in children under five occur in developing nations, including India.

Vaccination Recommendations and Current Challenges

H3N2 is known for its enhanced mutation rate compared to many other influenza viruses, which can diminish the immunity provided by past infections or vaccinations. This characteristic may explain the recent spikes in hospitalizations associated with H3N2 in various countries, including the United Kingdom and the United States. The WHO recommends annual flu vaccinations for pregnant women, children aged six months to five years, individuals above 65 years, those with chronic health conditions, and healthcare workers.

In India, the Indian Academy of Pediatrics (IAP) advises that flu vaccinations should be given annually to children aged six months to five years, along with individuals in high-risk categories. However, the uptake of influenza vaccines among children and older adults in India has historically been low. Since these vaccines are not part of the government-operated Universal Immunisation Programme (UIP), they are primarily offered in private healthcare settings, with costs ranging from Rs 2,000 to Rs 2,500 per shot.

Current influenza vaccines have shown about 50 to 60 percent effectiveness. Although this level of effectiveness can considerably mitigate severe illness, hospitalizations, and mortality, experts suggest that the seasonal flu vaccine might offer protection against H3N2 alongside other circulating strains. India typically experiences two peaks of seasonal influenza each year: one from January to March and another during the post-monsoon period. With updated vaccines targeting H3N2 expected to be available, vaccination will likely benefit a significant segment of the population. In addition, established preventive measures, such as wearing masks when ill and practicing frequent hand hygiene, remain crucial in controlling the spread of influenza.

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