H1N1 Flu Vaccine: WHO Says 1 To 2 Billion Doses Could Be Produced

Should global vaccine production be required, then 1 to 2 billion doses could be made to combat the new H1N1 flu virus, said officials from the World Health Organization (WHO) on Wednesday, just before the global health agency released the latest count of 1,893 confirmed cases in 23 countries and 31 deaths (29 in Mexico and two in the US).

Dr Marie-Paule Kieny, WHO director of the Initiative for Vaccine Research, said in a press briefing that current world capacity for vaccine production is about 900 million doses a year and this could be scaled up to 1 to 2 billion for the H1N1 vaccine. Also, it would be between 4 and 6 months before the first batches were ready.

A WHO policy advisory committee is meeting later today to decide whether to ask vaccine producers to go ahead and start making vaccine against the H1N1 swine flu strain. If they agree to do so, they will advise WHO Director General Dr Margaret Chan to make a formal request to the manufacturers.

Kieny said experts were still uncertain about whether one or two doses would be needed per person for the vaccine to be effective. For the deadlier H5N1 strain of avian flu it was decided that two doses would be needed, but for this new H1N1 strain, “nobody knows”, said Kieny.

It may be that the population has already been “primed” against H1N1 to some extent from previous exposures to the human version, she said, and because of that they have some “background level” of immunity.

“If this is the case, it may be that one dose will be sufficient,” said Kieny, emphasizing however, that “this still needs to be demonstrated”, and that will only be possible in clinical trials in human as the first doses become available.

The number of doses required per person is important to know because if it is two then the global capacity will only be enough to treat half the number of people that could be treated if only one dose were to be required.

It will be one or two months before experts know whether it will be one or two doses, said Kieny.

Before the manufacturers can start producing the vaccine they need what is called “seed strains” or “vaccine strains” of the virus. These are already being made in WHO collaborator labs and also in the US Centers for Disease Control (CDC) labs from collected isolates of the virus.

Kieny said the vaccine strains could be ready by the middle of May and the WHO will be posting the exact date and the labs from which the seed strains can be obtained on its website.

WHO have already spoken to manufacturers and assured them that all vaccine producers will be able to get the seed strain and they only need apply to WHO collaborative labs to obtain them.

On the 19th May in Geneva there will also be a meeting with the heads of all the vaccine producers, the WHO and the United Nations to discuss how to “ensure more equitable access for developing countries to this vaccine when it becomes available,” said Kieny.

Manufacturers, the WHO and the UN are also discussing how UN agencies such as UNICEF, who supply medicines to developing countries, will be able to purchase the vaccine as it comes off the production line.

Kieny said the manufacturers have been very “forthcoming” in discussions so far and was optimistic about having agreements ready to sign in a matter of weeks.

A big decision that still needs to be made is whether manufacturers should be asked to halt production of the seasonal flu vaccine. Kieny said there was not enough evidence yet to make this decision, but in the meantime the data is still being collected on the circulating seasonal strains, and plans are being prepared in case there should be a stop, but nothing is yet decided. It could be a matter of weeks before such a decision can be taken, she said.

In a briefing on Tuesday, Dr Keiji Fukuda, WHO Assistant Director-General ad Interim for Health Security and Environment, said that the people being infected by the new H1N1 strain are predominantly younger people. Although the age range of case includes the very young and the very old, the median age is 16. The virus is infecting men and women at the same rate.

Fukuda said that it was not unusual for this to happen with flu, that the first group to be affected tends to be younger adults, and then more and more of the rest of the population starts to become infected.

In that briefing Fukuda also answered a question about why there is so much concern about this particular virus when seasonal flu kills people every year. Fukuda said, yes, season flu kills about half a million people a year around the world, and most of them are either very young, very old, or already quite sick.

But the reason to be concerned about this new strain is that we already know a lot about the seasonal flu strains, they have been around for many years, and:

“We know that most people have had previous infections and have some immunity to them; that is what makes them seasonal influenza viruses,” said Fukuda.

“But we also know that when a new influenza virus enters into the human population, and people do not have immunity to this virus, then the levels of serious illness and the levels of death can be higher than we see with regular seasonal influenza,” he added.

Fukuda explained that it was the unpredictability of a new strain that is of concern.

While some previous new flu strain pandemics have not killed as many people as seasonal flu (for example the 1968 pandemic), some of them have killed a lot of people (like the 1918 pandemic which killed 20 to 40 million people). Also, the infections can be mild in the spring and then become more severe when the winter sets in.

“We want everyone to understand that what we see now is important, but to remember that this is a virus, this is situation in which things that evolve, and which things can evolve quite differently and that is why quite much attention is being taken to pay attention to what is going on,” said Fukuda.

“This is why we are jumping so hard on it because if it stays mild and people stay healthy, then that is great, that is the best possible outcome,” he added.

But if starts becoming severe, then we have to know about it and be prepared for it, he said.

Main source: WHO.

Written by: Catharine Paddock, PhD