The World Health Organization may have inadvertently triggered a new wave of fear over the threat of a swine flu pandemic today by suggesting that up to 2 billion people could be infected if the current outbreak worsens.
"If the situation continues to evolve and the virus does become established in other countries, and we do move into a pandemic, we would expect the virus to infect many people," said WHO chief Keiji Fukuda at a press conference today. "Perhaps a third of the world's population could be infected with this virus, based on previous pandemic."
Fukuda quickly noted to reporters that he was making statement based on data from past pandemics and was not a predicting what would happen with the current swine flu outbreak.
"I do not want you to walk out of here saying that there is an estimate that 2 billion will get infected in the next year or so," he said. "Please do not interpret this as a prediction for the future."
The comment immediately ignited debate among infectious disease experts.
"I think that WHO could serve the world health better by providing a more evidence-based, sensible 'benchmark' of H1N1 infection," said Ed Hsu, associate professor of public health informatics at the University of Texas School of Health Information Sciences and School of Public Health. He argued that the 2 billion figure, based on past pandemics, does not take into account recent public health improvements. Moreover, his own research has suggested that the rate of swine flu infection in the United States may have already stabilized.
"One could reasonably question the reliability of WHO's statement of mass infection," he said. "By making such statement without strong backing WHO may risk putting its accountability on the line."
On the other side of the argument is Dr. Christian Sandrock, assistant professor of clinical medicine in the Division of Infectious Diseases at the UC Davis School of Medicine. He said the numbers cited by Fukuda are less important than the overall message, which is that we should be prepared for a second wave of swine flu later this year.
"I think this is an important discussion -- not the numbers, but the likelihood of larger spread in the second wave," he said, adding that such a discussion is crucial for vaccine development and other issues of preparedness. "Much better to do this now than later."
The Swine Flu Vaccine Question
Still, the question of whether the public and the medical community should worry about a possible swine flu pandemic has big implications for preparing for such an event -- particularly in regard to vaccines.
As drug makers await the viral "seed strain" they need to begin manufacturing doses of swine flu vaccine by the millions, health officials are mulling what form the jabs might take -- and if Americans may be facing up to three needle jabs this fall.
The debate is not a trivial one. While infectious disease experts have said that there is much about the new strain of the H1N1 virus that they still do not know, government agencies must decide soon whether or not a swine flu vaccine will be needed -- particularly because such a vaccine would take months to develop and produce.
The risk of moving forward is that the virus will fizzle, making such a vaccine unnecessary. This would cost millions and, for pharmaceutical companies, waste precious time and resources.
The risk of delaying, on the other hand, is that the virus will resurge later this year and spread viciously through an unprotected populace.
Dr. Peter Katona, for one, believes one of these sets of risk far outweighs the other.
"To have a non-pandemic and waste the effort is worth it, compared to having a pandemic and not being optimally prepared," said Katona, an associate professor of clinical medicine at The David Geffen School of Medicine at UCLA.
"It would take a brave soul to operate under the impression that we're not going to see this [swine flu] again in the fall," agreed former CDC director Dr. Julie Gerberding. "Ideally, we want a just-in-case vaccine. Even it is no worse than seasonal flu, we will want a vaccine."
Drug makers already are preparing for such an effort. Pennsylvania-based Sanofi-Pasteur, the only U.S.-based manufacturer of injectable seasonal flu vaccine, said that it is in daily contact with the U.S. Centers for Disease Control and Prevention, waiting for the green light to begin the process.
"We expect in the next couple of weeks that the decision will be reached to make a pandemic flu vaccine," said Rick Smith, vice president of Strategic Programs and Projects for Sanofi-Pasteur. "Right now, we're getting everything ready -- getting raw materials, getting eggs, assessing production schedules."
But the exact form which such a vaccine would take -- specifically, whether it is lumped into the usual seasonal flu vaccine or offered as a separate shot or series of shots -- is still in question. And while this detail may seem trivial to some, it could well determine how effectively it is used.
Three's a Crowd? Concerns of Multiple Jabs
The question of what form a swine flu vaccine might take hit headlines late Tuesday when The Washington Post reported that the Obama administration may be considering a vaccination plan this fall for Americans that would involve a battery of three shots, two of which would be against the new viral threat.
Dr. Greg Poland, director of the Mayo Clinic's Vaccine Research Group, said he believed a swine flu vaccine would almost certainly have to take this form.
"Three shots are definitely possible," he said. "I think it is the only route we can go."
Poland added that manufacturers are already in the process of making the seasonal flu vaccine in preparation for the next regular flu season. Adding protection from another viral strain into this vaccine would involve a new layer of approval from regulatory authorities -- a complex step that could cost precious time.
Dr. D.A. Henderson, a distinguished service professor at Johns Hopkins University and an infectious disease expert, agreed.
"The production of the trivalent seasonal vaccine is now under way and continuing," he said. "To me, it would make sense to advise giving one dose of the [seasonal flu vaccine] and two doses of the new H1N1."
But not all agree that this is the best option. Dr. Pascal Imperato, chair of the department of preventive medicine and community health at SUNY Downstate Medical Center in Brooklyn, N.Y., said that in a perfect world, one shot would serve a dual purpose of protecting against both seasonal and swine flu.
"The best option, if possible, would be to incorporate the H1N1 antigens into the usual annual vaccine and recommend only one inoculation," he said, adding as a caveat, "Whether or not this is scientifically feasible remains an open question."
Swine Flu Vaccine: Is It Worth It?
Another open question is whether the threat posed by swine flu actually warrants its own vaccination. As much media coverage that swine flu has generated over the past couple of weeks, case and casualty figures remain low when compared with other diseases.
"If [the U.S.] decided to make the vaccine investment," Hsu noted, "the administration would have to make a stronger case, at some point, why a disease that caused two deaths and less than 500 cases in the U.S. in a two-week period -- with a risk not greater than seasonal flu -- would warrant the multibillion dollar investment, versus other prevalent diseases such as hepatitis, cancer or [cardiovascular disease] that each caused dozens of thousand deaths and affects millions of Americans each year."
Dr. Harley Rotbart, professor of microbiology at the University of Colorado School of Medicine and author of the book "Germ Proof Your Kids -- The Complete Guide to Protecting (without Overprotecting) Your Family from Infections," said that the effort to produce a special vaccine would be a massive undertaking -- especially considering that such an effort would take place at the same time that companies are manufacturing seasonal flu vaccine.
"How to fit an 'emergency' additional vaccine into the mix without disturbing what we do well is ... [a] challenge," Rotbart said.
And even with all drug makers producing the vaccine, it is unlikely that there would be enough to protect everyone.
"World ability is about one billion doses," Poland said. "That is not enough. There are priority tiers on who gets vaccine. Little or no [vaccine] will go to underdeveloped countries."
Americans May Not Get Their Shots
Domestically, the questions over how many Americans will accede to three needle pokes instead of just one is another part of the equation, of course. In a Gallup poll released today, only 46 percent of respondents said they would get a swine flu vaccine shot if available, while 52 percent said they would not.
And though the medical community at large is in general agreement that vaccines are notably safe, the jabs are not without their possible side effects and risks.
Notably, during the 1976-1977 flu season, those who received a vaccine for swine influenza appeared afterward to have an increased risk of Guillain-Barre syndrome (GBS) -- a disease in which the body damages its own nerve cells, leading to muscle weakness and occasional paralysis. According to the CDC, between 5 and 6 percent of all patients with GBS die from it.
"Many will remember reports of this complication from 33 years ago, and most will certainly be reminded of it by the press and media," Imperato said.
Health officials emphasize that this risk is no longer an issue, thanks to improved safety testing and additional research. Still, many of those who remember the episode may be reticent to opt for the shot, some doctors worry.
"There is not enough time or a large enough sample to test any vaccine before we will need it this fall," Olds said. "That will create uncertainty and decrease coverage. ... Most people will likely not take it for fear of the neurologic side effects unless they are facing a major swine flu pandemic with a higher-than-currently-observed mortality rate. Most would prefer to sit back with some Tamiflu in their pocket and wait and see."
And then there is the question of whether people will be willing to visit the doctor multiple times for multiple shots -- particularly in light of the common complaint among infectious disease experts that not enough Americans get their single seasonal flu shot already.
Still, Henderson said he believes that even if vaccinating the public against both seasonal flu and the swine flu takes multiple jabs -- and multiple visits the doctor -- a properly conceived public health effort could protect much of the public from illness.
"I would speculate that the [seasonal flu vaccine] and one dose of the H1N1 could be given at the same time, but that needs to be confirmed," he said. "Thus, it might be possible to deliver the needed vaccine with just two visits.
"Yes, I've dealt with a number of vaccine campaigns, and I know the potential confusion that could and will result in some instances. However, this is not exactly rocket science. It can be done."
The ABC News Medical Unit contributed to this report.