Novel H1N1 means the so called pandemic swine flu virus. Seasonal flu vaccine (2009) means vaccine containing H1N1 strain of yesteryear and not novel H1N1 strain. Novel H1N1 has replaced to the tune of 90% all the flu viruses in areas where there has been documented novel H1N1 outbreak. This is also evident by the sero-epidemiological survey done in areas like Pune, where nearly 25% of the general population was found to be seropositive for the novel H1N1strain (most of them asymptomatic though). Hence in such areas it is futile to use seasonal flu vaccine made for use during 2009. This vaccine is of no use now as we await ‘seasonal’ vaccine for the year 2010.

In 2009, after the pandemic with novel H1N1, there was need to protect against the new virus (not covered by seasonal vaccine 2009). This is the reason why a monovalent novel H1N1 vaccine was ordered by WHO for immediate use in world. Now we have more than 5 monovalent novel H1N1 vaccines available in the world, including one in India (licensed for use only for >18 years of age individuals). These vaccines have been used in millions in the developed world since last 6 months. This is also the reason why WHO has now declared that novel H1N1 strain will be the only H1N1 strain in the seasonal vaccine, besides the H3N2 and the B serotypes for this year (2010).

Till the new trivalent vaccine containing novel H1N1 is available, one has to use monovalent H1N1 vaccine to protect against novel H1N1 infection. A live nasal monovalent novel H1N1 vaccine is going to be marketed soon in India for the use from 3 years of age onwards, and we hope to receive the ‘seasonal’ 2010 vaccine (containing the novel H1N1 strain) by September 2010. The IAP COI recommendations on use of any flu vaccine remain same as in past (including the novel H1N1 vaccine – monovalent or trivalent)(1)