"ICMR confirms no new H1N1 strain as seasonal swine flu cases rise"
Antigenic drift
gradual mutation of influenza surface proteins, requiring annual vaccine updates.
Antigenic shift
sudden exchange of genetic segments between two influenza strains, potentially creating a pandemic virus.
Influenza A (H1N1), commonly called swine flu, first emerged as a pandemic strain in 2009. The World Health Organization (WHO) declared it a pandemic that year, and the strain has since become part of the seasonal influenza cycle worldwide. In India, the National Centre for Disease Control (NCDC), under the Union Health Ministry, maintains a nationwide influenza surveillance network. It tracks case counts, deaths, and circulating strains across states, and publishes treatment and prevention guidelines. The Indian Council of Medical Research (ICMR), established in 1911, is India's apex biomedical research body. It conducts virological surveillance, identifies circulating strains, and advises on vaccine composition. Together, ICMR and NCDC form the institutional backbone of India's influenza response.
Seasonal influenza vaccines are updated annually based on WHO strain recommendations for the Northern and Southern Hemispheres. India follows the Northern Hemisphere recommendations. The recommended vaccine is typically a trivalent or quadrivalent formulation covering H1N1, H3N2, and one or two influenza B lineages. Vaccine effectiveness depends on how closely the vaccine strains match the circulating strains, a concept called antigenic match. When match is good, vaccines significantly reduce hospitalisation and death, especially in high-risk groups.
Influenza A viruses are classified by two surface proteins: haemagglutinin (H) and neuraminidase (N). H1N1 refers to a subtype carrying H1 and N1 proteins. Within subtypes, viruses are further grouped into clades and subclades based on genetic evolution. The currently circulating Indian strain belongs to clade 6B.1A.5a2a, subclade D.3.1.1, and is designated A/Missouri/11/2025 (H1N1) pdm09-like virus. The suffix "pdm09" indicates descent from the 2009 pandemic strain.
Vaccine development for influenza follows a well-established principle: the immune system is exposed to a harmless form of the virus antigen, prompting it to produce antibodies. For influenza, this is done using inactivated virus particles or specific viral proteins. Because influenza viruses mutate rapidly, a process called antigenic drift, the vaccine composition must be reviewed and updated each year. …
H1N1 virus is sometimes mentioned in the news with reference to which one of the following diseases?
What is the basic principle behind vaccine development? How do vaccines work? What approaches were adopted by the Indian vaccine manufacturers to produce COVID-19 vaccines?
In the context of vaccines manufactured to prevent COVID-19 pandemic, consider the following statements:
1.The Serum Institute of India produced COVID-19 vaccine named Covishield using mRNA platform.
2.Sputnik V vaccine is manufactured using vector based platform.
3.COVAXIN is an inactivated pathogen based vaccine.
Which of the statements given above are correct?
What is the importance of using Pneumococcal Conjugate Vaccine in India?
1.These vaccines are effective against pneumonia as well as meningitis and sepsis.
2.Dependence on antibiotics that are not effective against drug-resistant bacteria can be reduced.
3.These vaccines have no side effects and cause no allergic reactions.
Select the correct answer using the code given below:
With reference to Influenza A (H1N1), consider the following statements:
1.H and N in H1N1 refer to haemagglutinin and neuraminidase, the two surface proteins of the influenza virus.
2.The suffix 'pdm09' in the strain designation indicates that the virus is descended from the 2009 pandemic strain.
3.Antigenic shift refers to gradual point mutations in influenza surface proteins, requiring annual vaccine updates.
Which of the statements given above are correct?
Assertion (A): ICMR's confirmation that the circulating H1N1 strain in India matches the 2025-26 vaccine strain means existing vaccines are effective against the current outbreak.
Reason (R): Influenza vaccine effectiveness depends critically on antigenic match between the vaccine strain and the circulating strain.
Which of the following is correct?
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