The Centers for Disease Control and Prevention (CDC) said that the voluntary recall, which affects some 800,000 doses, is not related to any safety concerns and stressed that the vaccine is still expected to elicit a protective immune response.
The CDC also stressed that children who have already received the vaccine, which was shipped in November, do not need to receive a second shot apart from those aged under 10 in whom two doses of vaccine are recommended anyway.
To date, only Maryland and Virginia have confirmed they received vaccines from one of the affected lots, UTO23DA, UTo28DA, UTo2CB and UTo30CA, but neither could said how many doses had been used.
While the recall is obviously a concern for Pasteur and its French parent Sanofi Aventis, of perhaps more significance is its likely impact on public confidence in influenza vaccines, particularly those for H1N1 or “swine flu”.
Despite considerable public demand when the World Health Organisation (WHO) declared the H1N1 pandemic in June, anecdotal reports suggest that influenza vaccine uptake has been lower than expected.
Part of the problem is the perceived lack of severity of the circulating H1N1 virus which, while still responsible for significant numbers of deaths worldwide, has not hit the figures some predicted when the pandemic began.
There is also a vociferous anti-vaccination lobby, which has raised concerns that regulatory dispensations used to accelerate production mean that the available H1N1 vaccines have not been subjected to the same safety assessments.
This idea is reflected in a September survey by the Harvard School of Public Health’s opinion research program, which revealed that concerns about potential side effects was the leading reason (38 per cent) respondents said they would not the vaccination.
Unfortunately, this type of opinion is likely to be re-enforced by the Sanofi recall, which follows hot on the heels of a GSK request that Canadian authorities do not use 172,000 doses of its H1N1 vaccine.