Clinical trials of newly developed vaccines for swine flu have begun in the USA and Australia. These human studies will gather data on the safety and effectiveness
Clinical trials of newly developed vaccines for swine flu have begun in the USA and Australia. These human studies will gather data on the safety and effectiveness of the vaccine.
The National Institute of Allergy and Infectious Diseases (NIAID), which is part of the National Institutes of Health in the USA, announced yesterday that a network of medical research institutions is about to begin a series of clinical trials to gather safety and efficacy data about some of the new influenza vaccines.
At a special meeting of the Strategic Advisory Group of Experts (SAGE) on July 07 2009, the WHO considered the potential options for vaccine use. They came up with some recommendations that were endorsed by the WHO Director-General, including:
To make a vaccine, a large amount of the virus or bacteria is needed. In the case of swine flu, the US Centers for Disease Control and Prevention (CDC) began isolating and preparing strains of the swine flu virus as soon as the first human case became known. These strains were sent to its counterparts in other countries including the National Institute for Biological Standards and Control (NIBSC) in the UK. These organisations prepare the virus strains to be used in making the vaccine.
Viruses can be grown in hens’ eggs, but often the infectious influenza virus strains do not grow well in eggs. To get around this, the infectious virus is injected into the eggs with another influenza virus that thrives in eggs. The two viruses swap pieces of their genetic material and produce hybrids, some of which both grow well in hens’ eggs and also have the elements of the disease-causing virus needed for a vaccine. These hybrids are isolated and the best candidate for making a vaccine is selected. This chosen hybrid strain is then grown and distributed to vaccine manufacturers.
The vaccine manufacturers use dead or weakened virus to create the vaccine. Other constituents can also be added to the vaccine, such as a suspending fluid to carry the virus into the body, preservatives and stabilisers that allow the vaccine to be stored safely, and chemicals to help the vaccine to promote an immune response.
Vaccine development usually takes about six months and it began in April 2009. The WHO suggests that the first doses of influenza A H1N1 vaccine are expected as early as September 2009. The UK government says that the first batches of vaccine are expected to arrive in the autumn, and 30m double doses (enough for half the population) are expected to be available by the end of the year. The government has ordered enough vaccine for the whole population, and when it becomes available will focus on those at the greatest risk first.
The administration of the vaccines will need to be prioritised. The decision on prioritisation of the population will be taken on the basis of which groups are being most affected by the virus, when the vaccine arrives and how best to protect the NHS from being over-stretched.
Vaccination is very effective in preventing and reducing the impact of serious illness. Although vaccines are not 100% effective and can become less effective if the virus mutates, they still offer some protection. Current flu vaccines last for about a year and give about 70-80% protection against infection with strains of influenza virus that are very similar to those used to make the vaccine. It is too early to predict how the swine flu virus might mutate. The WHO is closely monitoring it for changes, and this will help countries to make a quick response if the virus undergoes important changes.
The human trials that are currently underway will provide some evidence of the short-term safety and effectiveness of the vaccines. In particular, the researchers will be monitoring side effects and also how effectively the vaccine prompts a response from the immune system (its immunogenicity). The vaccines will be approved for use by national authorities. In this country the Medicines and Healthcare products Regulatory Agency (MHRA) is responsible for monitoring the safety of flu medicines and vaccines. Safety monitoring will be ongoing once the vaccine programme is introduced.