Vaccination gets the green light

Fergus Walsh | 17:42 UK time, Friday, 16 October 2009

The long-awaited UK-wide programme of vaccination against H1N1 swine flu will begin next week.

The first to get immunised will be the most vulnerable people in the population - namely, high-risk patients in hospital (for example, those with leukaemia who have a weakened immune system).

The Chief Medical Officer for England, Sir Liam Donaldson, who is the government's main advisor on tackling the virus, gave further details (for England) at his weekly press briefing.

The GSK vaccine Pandemrix has become the jab of choice for the NHS, despite the government also buying stocks of a second vaccine Celvapan, from another manufacturer, Baxter. This is partly due to production problems with the Baxter vaccine.

Sir Liam Donaldson urged at risk groups, including pregnant women, to get immunised:

"I don't want to see anyone dying of an illness that can be prevented by vaccination. Only this week we have seen two deaths among pregnant women: one in Scotland and another in Wales."

The head of immunisation at the Department of Health, Professor David Salisbury, said those over 10 years of age would need just one dose of Pandemrix vaccine, because clinical trials had shown that it was sufficient to offer good immunity.

Those under 10 will need two jabs, spaced three weeks apart, because their immune systems don't respond as well.

By contrast, anyone who has Celvapan will require two doses. Professor Salisbury said he specifically wanted pregnant women to have the Pandemrix GSK jab, because it meant they would be protected quicker. He said:

"If a pregnant woman has an interval of three weeks to wait for immunity to kick in, that could put the pregnancy at risk, so it is seriously beneficial for them to be protected after one dose of Pandemrix."

Professor Salisbury pointed out that both vaccines had been licensed and were safe. The Baxter vaccine, which is not made using eggs, would be used for those who have a rare egg allergy. The key difference between the two vaccines is that Pandemrix has an adjuvant, or booster chemical, which is designed to boost the body's immune response.

Adjuvanted flu vaccines have been around for at least a decade, but there is not nearly the same degree of clinical data as with unadjuvanted flu jabs.

Because of the lack of clinical data, the WHO suggested in July [267KB PDF] that swine flu vaccines without adjuvants, should be used in pregnant women, where possible.

This suggestion came from the influential Strategic Advisory Group of Experts on Immunization (Sage). That would have meant Celvapan being used, not Pandemrix.

But Professor Salisbury, who chairs Sage as well as being the head of immunisation at the Health Department, indicated that this advice was now out of date.

"It was made before the GSK vaccine was licensed and based on what we knew at the time. The regulators were able to look at studies involving pregnancy in animals and at other clinical data."

SAGE meets in two weeks and is expected to revise its earlier guidance. So what should pregnant women do?

The clear advice is that those who are pregnant should be immunised because they are at considerably higher risk, as a result of the body's natural suppression of the immune system.

The further along the pregnancy, the greater the risk to the mother and her unborn child. Earlier this week, a pregnant teenager in Scotland died after contracting swine flu, leading to the death of her unborn child. Recently, a new mother in Wales died two weeks after giving birth following infection with the virus.

Many will want to find out as much information as possible about Pandemrix before agreeing to be immunised. There have been clinical trials - including data published today.

To date, 2,000 people have received the jab. None of those was pregnant because ethical committees will not usually allow pregnant women to take part in trials.

So what is in the adjuvant, known as AS03, found in the GSK jab? The key ingredient is something called squalene, which is derived from fish oil. The World Health Organization has an explanatory note on this.

Squalene (wikipedia) has been used in flu vaccines before, as the WHO makes clear:

"22 million doses of Chiron's influenza vaccine (FLUAD) have been administered safely since 1997. This vaccine contains about 10mg of squalene per dose. No severe adverse events have been associated with the vaccine."

and WHO say

Are squalene-containing vaccines safe?

• Over 22 million doses of squalene-containing flu vaccine have been administered. The absence of significant vaccine-related adverse events following this number of doses suggests that squalene in vaccines has no significant risk. This vaccine has been given primarily to older age groups.
• As this vaccine and new squalene-containing vaccines are introduced in other age groups, post-marketing follow-up to detect any vaccine-related adverse events will need to be performed.

GSK has a briefing note on its H1N1 swine flu vaccine.