The first doses of swine flu vaccine will be given to the public before full data on its safety and effectiveness become available, doctors confirmed yesterday.
The aim is to provide maximum protection against the pandemic in the shortest possible time.
But, unlike seasonal flu vaccine, the pandemic version will be spread over two doses in a higher quantity, and one brand is expected to contain a chemical additive to make it go further, potentially increasing the risk of side-effects.
Children, who are most vulnerable to swine flu and are likely to be among those first in line for the jab, may get the vaccine more than a month before trial results are received.
Adam Finn, professor of paediatrics at the University of Bristol and an expert on vaccination who will be testing the pandemic vaccine, said: "There will be a period where a risk judgement will have to be made. It will depend if there is an increase in the number of cases and deaths. Children are potent spreaders [of the virus] – they are now seen as the engine of the epidemic. We are dealing with information as it comes in – we could be dealing with a far worse epidemic, and we need to act sooner rather than later."
Yesterday it emerged that a baby aged under six months died at the Royal Free Hospital, London, last week and a 39-year-old mother who was reported to have given birth died at Whipps Cross Hospital, east London, on Monday. The Department for Children, Schools and Families said 1,000 schools had been affected by swine flu and some could be forced to stay shut after the summer holiday if the number of cases escalates.
The pressure to protect the population from the growing pandemic, and the short time available for production and testing of the vaccine since the H1N1 virus was identified in May, mean the licensing process is to be accelerated.
A previous vaccine against swine flu turned out to be worse than the disease. An outbreak in the US in 1976 infected 200 soldiers at a military camp in New Jersey, of whom 12 were hospitalised and one died. But before it was over 40 million people had been vaccinated, 25 of whom died and 500 of whom developed Guillain-Barre syndrome, an inflammation of the nervous system which can cause paralysis and be fatal.
Doctors said yesterday that today's vaccines are purer and cause fewer side-effects. Though the virus is mostly mild in its effects, it has claimed 29 lives in the UK and hospitalised 652 people in England. The NHS was ordered this week to plan for a worst-case scenario in which swine flu might cause 65,000 deaths over the coming winter, including several thousand deaths among children.
Discussions are still going on between the manufacturers, the European Medicines Evaluation Agency (EMEA), and the Department of Health over how much data will be required.
The Government has placed advance orders for up to 132 million doses of vaccine with two manufacturers, GlaxoSmithKline and Baxter. The manufacturers have tested and licensed in advance three "core" vaccines in preparation for a pandemic. These are vehicles into which the H1N1 pandemic strain of the virus is inserted.
A spokesman for the EMEA said the first samples of the fully functional pandemic vaccine were expected by the end of July and a decision on whether to approve them would be taken within five days. Trials involving 200 to 400 patients would be conducted, but the vaccine would be made available for use by the NHS before the results came in.
"What the manufacturers will be submitting will not have any clinical trial data. We expect the interim adult data from September and the first paediatric data from October onwards," he said.
Last night a spokesperson from the Department of Health defended the EMEA, saying : "The UK has one of the most successful immunisation programmes in the world.
"Appropriate trials to assess safety and the immune responses have been carried out on vaccines very similar to the swine flu vaccine. The vaccines have been shown to have a good safety profile. More than 40,000 doses of the vaccines which the swine flu vaccines are based on have been given without any safety concerns."