H1N1 Vaccine Update:

The global rise of H1N1 continues. Currently over 526,000 infections and around 6700 deaths have been confirmed. The Americas account for 72% of all deaths with around 4800 reported deaths. In contrast, while 166,750 cases are confirmed in the Western Pacific region, there are lower mortality rates here than in the Americas; 613 deaths are confirmed in this region ¹.

 

Severe symptoms of pandemic H1N1 2009 can result in hospitalisation and death. Virulence factors could associate pandemic H1N1 infections with more severe disease; H1N1 virulence factors have not been reported. Epidemiological data continues to indicate that pregnant women, young children under 5 years of age and individuals with chronic underlying conditions, (including respiratory problems, obesity and diabetes) are at significantly greater risk of severe disease symptoms than the wider population.

 

Specific H1N1 (swine flu) vaccines are being administered, but apprehensions about pandemic H1N1 disease severity and vaccination are re-iterated around the world. Concerns abound regarding whether pandemic H1N1 disease risk is great enough to warrant vaccination. Unease about vaccine safety and effectiveness is also frequently expressed.

 

The World Health Organisation (WHO) estimates that 80 million doses of H1N1 vaccine have been distributed, and an estimated 65 million cumulative doses administered. H1N1 immunization campaigns are in progress in 40 countries and regions. Dr Marie-Paule Kieny, Director for the Initiative for Vaccine Research at WHO commented that H1N1 vaccines ‘include different products, inactivated (virus) with or without adjuvant as well as live attenuated vaccines.’ To date there has been ‘no significant difference in the safety profile between different types of vaccines‘.

 

One adverse event is reported for every 10,000 H1N1 vaccine doses administered. From these adverse event reports, 5 out of 100 are considered serious. Less than a dozen cases of Guillain-Barre syndrome, (which was associated with H1N1 vaccinations in 1976) have occurred in association with 2009 H1N1 vaccines. Guillain-Barre syndrome disease was transient and all patients recovered. No deaths have been associated with H1N1 vaccines. While there have been around 30 reports of death after H1N1 vaccine delivery, none have been directly associated with these vaccines. 

 

The goal of vaccination is to increase individual and population-level specific disease immunity, reduce illness and mortality rates, and slow the spread of specific disease. Timing of vaccination is crucial in determining vaccine effectiveness. Studies have shown that H1N1 vaccines can generate specific immunity and indicate that responses will be effective against H1N1 ^{2 3}.

 

With the scale of infection, it remains important that all antiviral treatment follow medical advice in order to reduce the development and spread of H1N1 anti-viral drug resistance. Dr Nikko Shindo, a Medical Officer in WHO’s Global Influential Programme recommends prompt antiviral treatment when flu symptoms occur, particularly for individuals in at-risk groups. Medical practitioners are also encouraged to prescribe anti-viral medication to individuals not among at-risk groups when persistent or rapidly worsening symptoms occur. Such symptoms include vomiting, diarrhoea, difficult breathing and high fever lasting more than 3 days.

 

Whether or not you choose to get vaccinated, you can implement other H1N1 disease reduction measures. Those predicted to be at greater risk of severe disease are encouraged to be immunized, but if all at-risk individuals rushed out to get the vaccine in the coming days and weeks, most would have a very long wait. 

 

 

1. WHO. Pandemic (H1N1) 2009 - update 75. 2009;

http://www.who.int/csr/don/2009_11_20a/en/index.html

2. Greenberg ME, Lai MH, Hartel GF, Wichems CH, Gittleson C, Bennet J, Dawson G, Hu W, Leggio C, Washington D, Basser RL. Response after One Dose of a Monovalent Influenza A (H1N1) 2009 Vaccine — Preliminary Report. N Engl J Med 2009;

http://content.nejm.org/cgi/reprint/NEJMoa0907413.pdf?resourcetype=HWCIT

3. Clark TW, Pareek M, Hoschler K, Dillon H, Nicholson KG, Groth N, Stephenson I. Trial of Influenza A (H1N1) 2009 Monovalent MF59-Adjuvanted Vaccine — Preliminary Report. N Engl J Med 2009;

http://nejm.highwire.org/cgi/reprint/NEJMoa0907650.pdf