One-shot flu vaccine
Finally some good news about swine flu: the Swiss firm Novartis reports today that its pandemic flu vaccine works with only one shot. Half as much dead virus as in regular winter flu shots was needed to give 80 per cent of the adults injected the amount of immune reaction required for ordinary flu vaccines.
This is good news. The low dose of virus means more doses can be made in a short time, especially useful as the vaccine viruses are growing slowly.
But the best news is that one shot works.
Normal flu vaccine requires only one shot – but that is because it is essentially a booster for your existing immunity to flu you have encountered before. Vaccine research shows you need two shots of vaccine three or four weeks apart to immunise people against a flu strain they have never encountered before, either because they are children or because the flu is novel – as the pandemic H1N1 virus is to anyone born since 1957. Before then ordinary seasonal flu was also a H1N1. The 1957 pandemic replaced it with another type of flu virus.
Giving a lot of people one vaccination is already a logistical nightmare – making sure everyone gets two shots at the right time is vastly harder. Moreover if they need two shots to become immune, most people would not be protected until some six weeks after the first vaccination, possibly too late.
The Novartis announcement is not a complete surprise, as their vaccine is made using an immune stimulator called an adjuvant, already known to sometimes promote sufficient immunity to a novel flu in one jab and at low doses. But that may create problems for some countries.
The US is considered unlikely to use an adjuvanted pandemic vaccine, as it is rushing through the requisite regulatory approvals based on previous tests of similar vaccines, and no adjuvanted flu vaccine has ever been approved in the US. One is used in Europe, however, and a similar regulatory process is expected to permit adjuvanted vaccines there.
But adjuvants may not be the only answer. This week China approved two vaccines also said to elicit sufficient immunity in one shot, one by Hualan Biological Engineering of Xinjiang, the other by Sinovac in Beijing, a leader in flu vaccine development. The Sinovac vaccine contains a 15 microgram dose of split virus, and no adjuvant – much like pandemic vaccine now being tested in the US, for which results are expected in two weeks.
(By Debora MacKenzie | newscientist)
- Raquel Leoncio
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