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How did vaccines help in the pandemic?

NIHR studies showed that new vaccines, developed for the specific pandemic flu strain, were effective in protecting people.

Two different vaccines were developed to immunise against the new (H1N1) strain. More than one vaccine was needed, firstly to ensure a sustainable supply, and secondly to reduce the chance of an effective vaccine being unavailable.

One was an adjuvant vaccine - using part of the virus and an extra ingredient - to improve the immune response. The other used the whole virus to achieve a response.

Research showed that both vaccines gave people immunity to the H1N1 strain of flu, but that there were some differences.

Which vaccine worked best?

Two vaccine trials were carried out quickly, one in children and the other in adults. The results in the two age groups were broadly similar, with both producing a good immune response. The adjuvanted vaccine produced immunity in more people but it resulted in more adverse reactions, such as fever or pain at the injection site. For example, adjuvanted vaccine gave 98% of under threes immunity compared to 80% in the whole virus. But 22% of under-fives had a fever from the adjuvanted vaccine, compared to just 9% with the whole virus.

"The adjuvanted vaccine.. could induce immune responses which were better than we usually see in young children but with a quarter of the dose.

"This is especially important in the context of a pandemic where it may be necessary to spread as many doses as possible across a population, in order to try to protect as many people as possible."

Professor Andrew Pollard, University of Oxford

In adults, a similar pattern of greater benefit at the expense of an increase in reactions was seen, although overall the adjuvanted vaccine appears the best option and many adults will only need one dose.

Older people have a weaker immune response and the research suggested that they needed two doses of the H1N1 vaccine to develop immunity in the pandemic.

A larger study

As well as trials, NIHR funded the large VIPER study to observe the protection given by the vaccination programme implemented through a sample of general practices in Scotland. This compared flu and hospital admission rates in people who did, and did not, have the vaccine, adjusting for possible confounding factors such as gender, age, deprivation and risk due to morbidity.

This study was possible because of the good system of linked medical records in Scotland. It suggested that the pandemic flu vaccine was 95% effective in preventing flu and 100% effective at preventing complications, such as pneumonia requiring hospital admission. The limitations of the study may mean that the real benefit is slightly less than this, but the vaccine is likely to be very protective.

"An influenza pandemic, with the emergence of a new virus, provides huge challenges to the research community to identify rapidly safe and effective interventions that can reduce the impact of such a virus.  The mechanisms developed by NIHR play a key role in enabling that to happen.”

Dr Richard Pebody, Public Health England


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