Novel H1N1 2009 influenza pandemic has created widespread concern across the country. The virus continues to circulate and cause waves of infections leading to hospitalization and complication in different parts of our country even this year. There have been at least 2241deaths and 41,234 laboratory confirmed cases (testing is done only for severe cases hospitalized) till 5th September 2010; actual cases may be much higher as many are not tested. 1257 confirmed cases with 128deaths have occurred in the week ending on  5^th September 2010. Since April 2010, Maharashtra, Kerala, Karnataka, Gujarat and some other cities like Kolkata have shown  rise in confirmed cases due to novel H1N1 2009 influenza. This means that though WHO has declared  that the world is in post-pandemic phase, it does not seem to be the case in India at present. Also now that, novel H1N1 vaccines are available India, pediatricians are interested to know the need, schedule, route of administration and all other relevant information for their day to day practices.

In many parts of world, novel 2009 H1N1 virus transmission peak is over and WHO has declared that we are in post-pandemic phase. In this regard, WHO Statement(1) dated 10^th August 2010 on  pandemic influenza is relevant and reproduced below. 

“The world is now in the post-pandemic period. Based on knowledge about past pandemics, the H1N1 (2009) virus is expected to continue to circulate as a seasonal virus for some years to come. While the level of concern is now greatly diminished, vigilance on the part of national health authorities remains important. Such vigilance is especially critical in the immediate post-pandemic period, when the behaviour of the H1N1 (2009) virus as a seasonal virus cannot be reliably predicted.

For example, it is likely that the virus will continue to disproportionately affect a younger age group, at least in the immediate post-pandemic period. Groups identified during the pandemic as at higher risk of severe or fatal illness will probably remain at heightened risk, though the number of such cases could diminish. In addition, a small proportion of people infected during the pandemic developed a severe form of primary viral pneumonia that is not commonly seen during seasonal epidemics and is especially difficult to treat. It is not known whether this pattern will continue during the post-pandemic period, further emphasizing the need for vigilance.

WHO is today issuing guidance on recommended activities during the post-pandemic period, including advice on epidemiological and virological monitoring, vaccination, and the clinical management of cases. National health authorities are reminded that cases and local outbreaks of H1N1 (2009) infection will continue to occur, and in some locations, such outbreaks could have a substantial impact on communities”

Though there is lot of awareness and anxiety  amongst the people about the disease and the vaccine/s available, present situation does not warrant a panic situation. Seasonal influenza, which has in past caused morbidity and mortality all these years and for which vaccine have been available did not create such hype. Case fatality rate in pandemic influenza is not very high and it is estimated to be between  0.05 to 0.2%. Though the virus has high transmissibility it is not highly virulent. Ironically, people in high-income countries used their vaccine stockpiles reluctantly. Around 80% of people in the UK chose not to be vaccinated, many because they doubted they were at serious risk (2). However this is a perception and not a scientific fact.  

Various monovalent novel H1N1 vaccines were made available in the world and India and these vaccines have been used in the developed world since last 6 months. These vaccines are safe and as such should not be denied to any one demanding it. One can  consider the local epidemiology of the H1N1 2009 and use it on the patient after one to one discussion and informed consent.(3) Now trivalent inactivated influenza vaccines are available in India (and world of course) and one live trivalent vaccine in USA. These vaccine covers  Novel H1N1 component  and seasonal flu strains recommended for year 10-11 season. 

Dose and Route of administration

Live Vaccine – 0.25 ml of the reconstituted vaccine in each nostril with the syringe and adaptor provided with the vaccine vail.

Inactivate vaccine – 0.5 ml intramuscular (0.25ml for a child between 6months and 3 years)

Number of doses – one dose above 9 years

(2 doses 28 days apart in less than 9 year old who is vaccinated for the 1^st time)

Seasonal influenza 2010 and novel H1N1 influenza vaccines available in India:

1. A live monovalent novel H1N1 vaccine (Serum Institute of India). Immunogenicity, and safety of the vaccine has been established in pre-licensure animal and human studies
2. The inactivated novel H1N1 monovalent vaccine of  Zydus is licensed for use only in adults above the age of 18 years.
3. Trivalent inactivated vaccine containing the novel H1N1 strain are available now (Chiron, Solvay, Lupin, GSK and Sanofi Pasteur)The 2010--11 trivalent vaccines contain A/California/7/2009 (H1N1)-like, A/Perth/16/2009 (H3N2)-like, and B/Brisbane/60/2008-like antigens. The influenza A (H1N1) vaccine virus is derived from a 2009 pandemic influenza A (H1N1) virus.

Who should be administered the H1N1 vaccine?

The following high risk individuals should be vaccinated against novel H1N1(ACIP recommendations)

·         When vaccine supply is limited, vaccination efforts should focus on delivering vaccination to persons who:

o    are aged 6 months--4 years (59 months);

o    are aged 50 years and older;

o    have chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders (including diabetes mellitus);

o    are immunosuppressed (including immunosuppression caused by medications or by human immunodeficiency virus);

o    are or will be pregnant during the influenza season;

o    are aged 6 months--18 years and receiving long-term aspirin therapy and who therefore might be at risk for experiencing Reye syndrome after influenza virus infection;

o    are residents of nursing homes and other chronic-care facilities;

o    are morbidly obese (body-mass index is 40 or greater);

o    are health-care personnel;

o    are household contacts and caregivers of children aged younger than 5 years and adults aged 50 years and older, with particular emphasis on vaccinating contacts of children aged younger than 6 months; and are household contacts and caregivers of persons with medical conditions that put them at higher risk for severe complications from influenza.

Indian Academy of Pediatrics, Committee On Immunization (IAPCOI) Recommendations on seasonal influenza vaccination (4):

The novel 2009 H1N1 infection, hospitalization and mortality has been disproportionately high in healthy young children and adults(unlike the past seasonal influenza outbreaks).Hence IAPCOI recommends to offer 2010 trivalent vaccine (inactivated or live) to high risk children as given below and any one who desires it(Live influenza vaccines are contraindicated in these group of individuals)

At risk individuals include:

• Congenital or acquired immunodeficiency

• Chronic cardiac, pulmonary, hematologic, renal, liver disease and diabetes mellitus

• Children on long term aspirin therapy

• Any neurologic disease that might cause respiratory compromise or impair ability to handle secretions

• Asthma requiring oral steroids

• Elderly aged more than 65 years.

Who should not be given the live vaccine ?

2009 H1N1 LAIV should not be given to the following groups.

• children younger than 3 and adults 50 years and older • pregnant women, • anyone with a weakened immune system, • anyone with a long-term health problem such as - heart disease - kidney or liver disease - lung disease - metabolic disease such as diabetes - asthma - anemia and other blood disorders • children younger than 5 years with asthma or one or more episodes of wheezing during the past year, • anyone with certain muscle or nerve disorders (such as cerebral palsy) that can lead to breathing or swallowing problems, • anyone in close contact with a person with a severely weakened immune system (requiring care in a protected environment, such as a bone marrow transplant unit), • children or adolescents on long-term aspirin treatment. Individuals who are moderately or severely ill( might be advised to wait until complete recovery from the illness) • Guillain-Barré syndrome 

H1N1 LAIV and seasonal LAIV should not be given together.

Children Who Should Not Be Vaccinated With TIV

Those younger than 6 months;

Those who have a moderate to severe febrile illness;

Those who have a history of hypersensitivity, including anaphylaxis, to eggs, to any previous influenza vaccine dose, or to any of the vaccine components; and

Those who are known to have experienced Guillain-Barre´ syndrome (GBS) within 6 weeks after a previous influenza vaccination (whether influenza vaccination specifically might increase the risk for recurrence of GBS is unknown).

How many doses need to be given ?

In previously unvaccinated persons aged <9 years, 2 doses of seasonal influenza vaccine are required to induce immunity because young children typically have had limited exposure to influenza viruses and are not immunologically primed (i.e., they do not have preexisting antibodies). The lack of preexisting antibody cross-reactive with the novel influenza A (H1N1) virus among children and younger adults raises the possibility that 2 doses of vaccine (typically separated by >21 days) also will be needed to provide protection for persons in these age groups. Ongoing studies will provide additional information about the immune response vaccine, including which groups might need 2 doses.

REFERENCES

1. WHO. H1N1 in post endemic period. http://www.who.int/csr/disease/swineflu/notes/briefing_20100810/en/index.html accessed 23rd August 2010.
2. Pandemic influenza-(some) reasons to be cheerful?(Editorial) Lancet 2010; 376: 565
3. Yewale V, Choudhury P. Seasonal flu vaccine (Reply). Indian pediatr 2010; 47: 722
4. IAP Guidebook of Immunization. Individual vaccines. Available from: http://www.iapcoi.com/pdf/chapter04individualvaccines.pdf Accessed on August 24, 2010.

IAP Committee on Immunization

Chairperson-Dr.Panna Choudhury,   Convener-Dr.Vijay Yewale