With H1N1 and other influenza infections increasing across the country, demand for flu vaccines has also started rising. Various health platforms are reporting a sharp increase in requests for at-home flu vaccinations and rapid testing, as per the media reports, with vaccine sales reportedly reaching nearly three times the level seen during the same period last year and more than doubling from July.  But as flu activity rises, one question is becoming increasingly common: Who should get the flu vaccine, and is it still useful to get vaccinated after cases have already started increasing? According to Dr Sourabh Pahuja, Senior Consultant, Pulmonology, Amrita Hospital, Faridabad, the decision to get vaccinated depends less on the number of cases and more on an individual's risk of developing severe influenza.

Who Should Get The Flu Vaccine?

"With H1N1 cases on the rise, the same question my clinic gets asked is, 'Should I get vaccinated now?' It depends more on who is asking than the number of cases," says Dr Pahuja. Influenza can cause several uncomfortable days even in otherwise healthy adults. However, the consequences can be much more serious for people who are at higher risk of complications. "Influenza can bring a number of difficult days for a healthy young adult. For an older person, a pregnant woman or a person with damaged lungs, an infection can cause pneumonia, hospitalisation or respiratory failure," he explains.

H1N1 Is Still Part Of Seasonal Influenza

The term H1N1 is often associated with the 2009 influenza pandemic. However, the H1N1 strain continues to circulate as part of seasonal influenza. "H1N1 is more than just the virus associated with the 2009 pandemic. The new flu shots contain the A(H1N1)pdm09 strain which is what's going around now as seasonal influenza," says Dr Pahuja. Influenza viruses continue to evolve, while immunity from previous vaccination can decline over time. Therefore, having received a flu vaccine in the past does not necessarily mean a person remains protected indefinitely. "Influenza viruses evolve and vaccine-derived protection wanes over time so an outdated vaccination is not a lifetime protection," he adds.

How Effective Is The Flu Vaccine Against H1N1?

The vaccine does not provide 100% protection against influenza, but evidence suggests that it can reduce the risk of severe disease and hospitalisation. According to Dr Pahuja, data from eight Southern Hemisphere countries during the 2025 influenza season showed that vaccination was about 42% effective in preventing hospitalisation specifically from H1N1. Preliminary data from the 2025-2026 season also indicated that vaccination reduced influenza-related hospitalisation by approximately 30% among adults and 41% among children and adolescents. "While these percentages are small, it means that fewer people are getting seriously ill, and that's clinically important," says Dr Pahuja.

Who Should Get Vaccinated?

Vaccination is particularly important for people who have a higher risk of developing complications from influenza. According to Dr Pahuja, vaccination is recommended for:

  • Adults aged 65 and above
  • Children below five years of age
  • Pregnant women
  • Healthcare professionals
  • People with asthma or COPD
  • People with diabetes
  • People with heart disease
  • People with extreme obesity
  • People with kidney disease
  • People with cancer
  • People with compromised immunity

These groups may be more vulnerable to complications such as severe respiratory infection, pneumonia and hospitalisation.

Why Is Flu Vaccination Important During Pregnancy?

Pregnancy deserves particular attention when it comes to influenza vaccination. "Pregnancy requires special attention. Vaccination protects the mother and also passes antibodies to the foetus," says Dr Pahuja. Influenza infection during pregnancy can be more serious, while vaccination can provide protection to both the mother and baby. "Studies have shown that immunising mothers decreases the incidence of influenza disease in infants under six months of age, who are too young to be vaccinated, by about one-third," he adds.

Is It Too Late To Get The Flu Vaccine If Cases Are Already Rising?

Ideally, vaccination should be completed before influenza activity begins to increase because the immune system generally needs around two weeks to develop protection after vaccination. "The shot should be given ideally before the expected flu surge because it takes about two weeks for the immune system to build protection. But that can still be useful, if cases are already being reported," says Dr Pahuja.

Therefore, people who are eligible for vaccination should not necessarily assume that rising cases mean they have missed their opportunity to benefit from the vaccine.

Does The Flu Vaccine Guarantee You Won't Get H1N1?

The influenza vaccine is not a guarantee against infection. Vaccine effectiveness can vary depending on factors such as the circulating strains, the match between the vaccine and circulating viruses, age and individual health. However, the primary benefit is reducing the likelihood of severe outcomes.

"The vaccination does not guarantee that you will not get the flu. Its more important role is to reduce the risk that an infection can turn into a medical emergency," explains Dr Pahuja. As H1N1 and other influenza infections increase, flu vaccination can be an important layer of protection, particularly for people who are more vulnerable to complications.

Older adults, young children, pregnant women, healthcare workers and people living with conditions such as asthma, COPD, diabetes, heart disease, cancer or weakened immunity should discuss influenza vaccination with their healthcare provider. And if flu activity has already started, it may not necessarily be too late. Since protection takes time to develop, getting vaccinated earlier is preferable, but vaccination during an ongoing flu season can still offer meaningful protection against severe disease.



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