January 6, 2011

experts react to the latest weekly national influenza report and questions on vaccine availability

The Health Protection Agency’s weekly figures on swine flu revealed that eleven more people died from swine flu in the previous week, taking the total to 50 for this winter. The release also addressed questions over whether enough vaccine had been made available.

Prof Ian Jones, School of Biological Sciences, University of Reading, said:

“1.,Are these numbers expected? Is it likely to be a continuing trend of increased cases and deaths – and will it be at the same rate?
“The numbers are not yet unusual. They are early and high but not at epidemic levels. No-one knows where they will go from here but the expectation is that they will peak and decline.”

2.,How does this compare with last year’s swine flu cases and how does it compare with normal seasonal flu (both in terms of numbers of cases and age of person)
“The numbers are still below the peak (first wave) of influenza seen in 2009. They are higher than has been typical for seasonal outbreaks in recent years but below a ‘bad’ year such as 2000.”

3.,Is it surprising that a number of these cases are from people who are not ‘at-risk’?
“Not yet. It’s the bell-shaped curve which will always produce some unexpected cases, some of whom may have undiagnosed underlying health conditions.”

4.,How is it that some people have previously had the vaccine (either this year or last year’s) but are still succumbing to flu?
“This is hearsay. If you have had the pandemic vaccine or the current seasonal vaccine you will not have been infected by the 2009 strain. You may well have had any one of several other respiratory illnesses which also spike at this time of year.”

5.,The vaccine is changed each year – is this vaccine better than last year’s? Is last year’s vaccine still effective for this year’s swine flu?
“The current vaccine includes the 2009 H1N1 and two other strains and is therefore as good as the pandemic vaccine for the predominant strain causing this year’s outbreak. Stocks of the pandemic vaccine, if available, will also protect against the major circulating strain.”

6.,Has the media coverage been fair? Seasonal flu doesn’t normally get huge amounts of media coverage, despite lots of deaths, so are we at risk of hyping this?
“It’s reasonable given recent interest in influenza. The public interest partly derives from the feeling that pandemic flu (swine flu) had ‘been and gone’ despite many commentators suggesting we would see it again this year.”

Dr Tarit Mukhopadhyay, Lecturer in Vaccine Bioprocess Development, University College London, said:

“The flu vaccine is still primarily produced in chicken eggs, which means there is a significant lag time (approx. 6 months) to prepare the vaccine. This year manufacturers folded the H1N1 (swine flu) strain into the seasonal vaccine in order to deal with the predictable increase in seasonal swine flu cases. It would seem, however, that errors were made in not ordering enough vaccine from the manufacturers, correctly identifying the ‘at risk’ groups and deciding to drop the flu jab ad campaign.

“One can be sympathetic on the first two points, as orders would have to be placed months in advance without truly knowing how severe the new mutated strain will be. This is because every progeny virus is a mutant, and it can be difficult to predict how the virulence factors have changed. Dropping the ad campaign, however, has directly affected the uptake of the flu jab, especially because there is a certain amount of complacency with regard to seasonal flu.”

Dr John McCauley, National Institute for Medical Research, said:

“The vaccine is changed each year – is this vaccine better than last year’s? Is last year’s vaccine still effective for this year’s swine flu?

The vaccine recommended for use in the Northern Hemisphere is a tri-valent vaccine with an H1N1 component, an influenza H3N2 component and an influenza B component. The H1N1 virus is, or is antigenically similar to, the prototype vaccine virus A/California/7/2009 virus. The H3N2 virus is, or is antigenically similar to, the H3N2 variant that emerged in early 2009 A/Perth/16/2009. The influenza B virus is of the B/Victoria-lineage of influenza B viruses, or is antigenically similar to, A/Brisbane/60/2008.

“There had been no evidence for any significant antigenic drift of viruses when the global surveillance data were examined in September 2010 when the vaccine composition for the Southern Hemisphere 2011 was recommended and remained the same as recommended for use in the current Northern Hemisphere season. We are expecting the vaccine to be no less effective than last year.

“I believe the major use of the vaccine last year was the pandemic vaccine in the majority of cases in UK.”