Creating a vaccine against a pandemic flu before a pandemic flu occurs is impossible. Only shortly before pandemic flu breaks out would we know for what we need to make a vaccine! The World Health Organization states that at least at the very beginning of a pandemic, a vaccine would not be available.
Researchers are working on the development of a vaccine against the H5N1 subtype of the avian influenza virus, commonly known as bird flu. WHO warns that a H5N1 is the most likely candidate father of a pandemic. However, at this time, the form of the virus is not the one that would cause pandemic flu. The current form of H5N1 lacks efficient transmissibility, it's not very contagious, and therefore doesn't comply with the criteria necessary to cause pandemic flu.
The WHO cites some complications in creating an effective influenza vaccine quickly and distributing it where it is needed:
- Flu vaccines are currently cultivated in eggs. 1 infected egg provides enough virus for approximately 1 vaccine. In case of a pandemic flu coming from a deadly avian flu, the availability of eggs could be in jeopardy since laying hens would be affected.
- Roughly 300 million doses of the seasonal flu vaccine are produced each year. The world population today exceeds 6 billion.
- In case of pandemic flu, using the current methods to produce flu vaccine, two doses would be needed to achieve immunity.
- It takes four to six months to produce the seasonal flu vaccine stock. After a pandemic flu breaks out, WHO predicts that it will have found its way all over the world in a matter of a couple of months.
- 90% of production is based in Europe and North America, unlikely to be the locations of the initiation of a pandemic and home to only 10% of the world's population.
- Flu vaccines are expensive.
- The seasonal flu kills 250,000-500,000 people each year.
- Seasonal flu vaccine production would have to be stopped to produce pandemic flu vaccine should a pandemic flu break out.
And here are some novelties that may make speed up vaccine production, reduce the quantity of viral antigen needed to make a vaccine and make a more effective vaccine:
- Research is being done on producing vaccine by reverse genetics, reducing the time to prepare the vaccine seed viruses.
- Adjuvants, can mean that only a fifth or a tenth of the viral antigen would be needed to make a vaccine dose. So one egg could provide five or ten doses instead of just one. Some adjuvants being researched may be able to allow for the manufacture of a vaccine using 100 times less virus, meaning a cheaper, faster process.
- Live virus vaccines (such as the seasonal flu spray vaccine administered nasally) are more effective than the flu shot in people who have never been exposed to the virus. It's also easy to administer. These aspects are important in the case of a pandemic flu when vaccines will have to be distributed and administered quickly to a virus to which no one will be immune.
- A universal flu vaccine, one that protects against all types of influenza viruses may be possible by creating vaccines to parts of influenza viruses. The hemagglutinin protein of the virus is the one that changes the most and the one that human immune systems react to the best to create a protective immune response. Genetically engineered viruses that contain genetic material to produce a variety of antigens may generate an immune response against most influenza viruses. Unfortunately, it looks as though the reality of a universal influenza vaccine is not just around the corner.
SOURCES:
- Luke CJ, Subbarao K. Vaccines for pandemic influenza. Emerg Infect Dis [serial on the Internet]. 2006 Jan [date cited]. See paragraph "Developing Vaccines for Pandemic Influenza" See text http://www.cdc.gov/ncidod/EID/vol12no01/05-1147.htm;
- Palese P. Making better influenza virus vaccines? Emerg Infect Dis [serial on the Internet]. 2006 Jan [date cited]. See text http://www.cdc.gov/ncidod/EID/vol12no01/05-1043.htm
- Center for Disease Control. Avian Influenza Vaccine. Updated October 14, 2005. See text http://www.cdc.gov/flu/avian/gen-info/vaccines.htm
- World Health Organization. Vaccine Research and Development, Current Status. Nov 2005. See text http://www.who.int/csr/disease/avian_influenza/vaccineresearch2005_11_3/en/
The bibliographies of most of these articles are clickable and a treasure trove of original research papers regarding influenza vaccine research.