The annual production cycle for influenza vaccine
Introduction
The acute respiratory illness known as influenza appears to have afflicted humans since ancient times. Hippocrates described an influenza-like epidemic in 412 BC and numerous similar episodes have been described since then. They were once widely believed to be the result of adverse astrological alignments or other occult influences. In 1933, a virus was identified as the causative agent by Smith et al. [1]. The first inactivated influenza vaccines were introduced in the 1940s. Since then, vaccine companies have developed expertise in a safe and effective vaccine manufacturing process, allowing production of an increasing number of doses of the influenza vaccine each year. This article briefly reviews this production process.
Section snippets
WHO epidemiological surveillance
The hemagglutinin (HA) and neuraminidase (NA) surface glycoproteins of influenza viruses change frequently as a result of genetic mutation. For this reason, the World Health Organization (WHO) coordinates an international surveillance system to monitor the epidemiology of influenza viruses [2]. This system, established in 1947, allows for the detailed analysis of circulating influenza viruses isolated from both humans and animals, especially birds and pigs, and is able to detect newly evolved
Vaccine manufacturing timetable
Once the virus strains to be included in next season’s vaccine have been determined, candidate high-growth seed strains must be prepared by the WHO Collaborating Centers, tested by the manufacturers and put into production. Several factors govern the vaccine production timetable. First, manufacturers must undertake two production cycles each year; one each for the Northern and Southern hemispheres. Second, timing the delivery of vaccine is crucial because annual vaccination programs are
Characterizing the strains used for vaccine production
Currently, two subtypes of influenza A virus (H3N2 and H1N1) and one strain of influenza B virus are responsible for outbreaks of human disease and are, therefore, included in influenza vaccines. During the period since influenza A (H3N2) viruses re-emerged in 1968, the A (H3N2) strains chosen for the vaccine have been changed twice as often as have the strains for the other two influenza viruses. During the 21-years period from 1980/1981 to 2001/2002, 14 strains changes were made in the
Conclusions
The production of influenza vaccines requires careful coordination of a highly complex process involving a wide range of technical expertise in both public health laboratories and vaccine companies in order to provide on time safe and effective vaccines. Its remarkable success is self-evident; within two 6-month production periods, almost 250 million doses are brought to market in more than 100 countries each year [8]. The process of producing influenza vaccine can be expected to become even
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A virus obtained from influenza patients
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