Providers Brace for Swine Flu Revival
H1N1 Vaccine Moving Forward
Even as the rate of new 2009-H1N1 infections dwindles in the Northern Hemisphere, infection officials are bracing for the influenza's potential re-emergence this fall.
Efforts are underway to develop a vaccine for 2009-H1N1. "We're taking those initial steps that are important and necessary should a vaccine [for 2009-H1N1] need to be made," said Dr. Richard E. Besser, acting director of the U.S. Centers for Disease Control and Prevention. "There are a lot of decisions that need to be made between now and" this fall, when people start receiving their flu shots.
Current gaps in knowledge about 2009-H1N1 are expected to be filled in the coming months as the flu season unfolds in the Southern Hemisphere. During this time, he said, epidemiologists will be seeking answers to several questions: How does the virus compete with other viruses that are circulating in the community? Does it change, and if so, in what way? Does it develop resistance?
If given the go-ahead, the bulk of vaccine production can start at the end of June, which means that the earliest a 2009-H1N1 vaccine will be available is in September, according to Klaus Stöhr, D.V.M., vice president and global head of Novartis Vaccines and Diagnostics Ltd. and former head of the World Health Organization's Global Influenza Program. Dr. Stöhr spoke at the international conference on Influenza Vaccines for the World held in Cannes, France.
Any decision to produce a vaccine for 2009-H1N1 "will be based on the best available science," and it's far too early to tell what kind of a dosing regimen would be required for such a vaccine, Dr. Besser added.
The number of inoculations necessary will depend on how potent the vaccine needs to be, explained Dr. William Schaffner, chair of the department of preventive medicine at Vanderbilt University, Nashville, Tenn.
In all likelihood, the 2009-H1N1 vaccine will require two shots to ensure immunity. Couple that with the logistics of providing the seasonal influenza vaccine and "the potential for confusion is vast," he said in an interview.
Because people get immunized against the flu in so many different settings, it will be difficult to keep track of which shots an individual has actually received.
It may help to make the 2009-H1N1 vaccine available only at public health clinics, but they are not staffed or organized to immunize a large portion of the population.
It will also be quite difficult to track side effects specifically from the 2009-H1N1 vaccine.
The good news is that "what we're seeing so far is a fair amount of stability in the virus," Dr. Besser said.
At press time, virus isolates from the United States, Canada, Germany, Mexico, the Netherlands, and New Zealand had been genetically sequenced and "all of the genes examined were 99%-100% identical.
This means it will be somewhat easier to produce an influenza vaccine," said Nancy Cox, Ph.D., chief of the influenza division at the CDC.
A lot could happen, however, between now and the fall.
"We could see the current strain fizzle out and never come back again. We could see the current strain come back as it currently is, or we could see it mutate and come back in a more severe form," Dr. Besser said at a CDC press briefing.
"What we need to do during this period is make sure that we're prepared as a government, as a public health agency, [and] that our laboratories are ready should this come back as a much more severe infection," he explained.
So far, the genetic analysis of H1N1 has shown no sign of the virulence markers found in the 1918 pandemic influenza strain, also an H1N1 type, Dr. Cox said at CDC press briefing.
She echoed the caution, however, that there is a great deal that is not understood about the 2009-H1N1 virus.
The 2009-H1N1 strain is "easily transmitted," with an attack rate of about 25%-30%, based on early analyses of person-to-person spread within families and households, said Dr. Anne Schuchat, the CDC's interim deputy director for science and public health programs.
That attack rate is comparable to what is usually seen among most seasonal influenza strains.
Given that rate of 2009-H1N1 transition, the swine flu outbreak serves as "a stark reminder of the unpredictability of the timing and of the speed by which the pandemic situation can change," Dr. Stöhr said.