A research team at Imperial College London has reactivated the MOSAIC study to investigate mutations in the pandemic H1N1 virus.
From the Daily Mail, January 9, 2011 [hat-tip BeWell]:
Professor Peter Openshaw, director of the Centre for Respiratory Infection at Imperial, said: ‘We have paid particular attention to whether the mutations are affecting how well the vaccine works and whether the slight mutations have led to it becoming more severe.’
Asthma specialist nurse Katy Odeadra, who works in the Chest and Allergy Clinic at St Mary’s Hospital, said: ‘All the talk among doctors and nurses dealing with swine flu cases is of a mutated form of the virus.’
The suspicion that the pandemic H1N1 virus has mutated in a functionally significant way is likely due to the strain on critical care resources. Many more people, especially middle-aged adults, have required heroic efforts to keep them alive this year as opposed to the last wave of the pandemic. There are a number of possible explanations for this phenomenon. But I believe that the most likely is that the virus circulating in the United Kingdom has changed such that it can now readily infect middle-aged adults. Previously, most of the outbreaks were among children. This is no longer true.
The case fatality rate (CFR) was higher among middle-aged adults last year. So, even if the virus has not become any more lethal, infection of a larger proportion of middle-aged adults will naturally lead to more severe and lethal cases.
As to whether the current flu vaccine protects against pandemic H1N1 virus currently circulating in the UK, we don’t know for sure because so few people there have been vaccinated. Thus far, we have not seen a similar pattern of infection in countries with relatively high levels of vaccination like Canada or the United States. However, it seems unlikely that the new virus will remain confined to the UK. Once the new strain reaches North America, the efficacy of the current vaccine (or lack thereof) should be readily apparent.