Swine flu expected next flu season: vaccines encouraged

ATLANTA —The novel H1N1 virus is expected to make a big impact in the coming cough-cold-flu season, though just by how much is hard to determine, noted Anne Schuchat, director of the National Center For Immunization and Respiratory Diseases for the Centers for Disease Control and Prevention, during a press conference held late last month.

Based on the course of the novel H1N1 virus in the spring, between 6% and 8% of people in those communities that were affected came down with the novel flu at a time when seasonal flu incidence is relatively zero. “In a longer winter season, attack rates would probably reach higher levels than that,” Schuchat said. “Maybe two or three times as high as that.” During seasonal influenza in the winter, as many as 15% of people develop influenza-like illnesses.

To put this into perspective, if the novel H1N1 virus has a run rate of 24% and is no more or less virulent than the seasonal influenza, that would suggest that more than 70 million Americans could come down with the flu this year, more than 320,000 could be hospitalized and more than 57,000 could even die from flu-like causes.

Worse-case scenario models used as pre-pandemic planning tools have accounted for as many as 40% of Americans to be infected, or to be tasked with caring for an infected relative, this fall, which is expected to cause mass absenteeism across schools and work forces.

However, there are a number of x-factors that make projecting the potential impact from a pandemic flu exceedingly difficult: the virulence of a constantly-mutating strain, whether or not a Tamiflu/Relenza-resistant strain becomes predominant, and the effectiveness of either the seasonal influenza vaccine or a novel H1N1 influenza vaccine.

The CDC also updated its H1N1 vaccination recommendations late last month, identifying five priority groups. These groups, in order, are: pregnant women, household contacts of those children less than 6 months of age (babies under 6 months of age cannot be vaccinated), healthcare professionals and emergency service personnel, children/adults between the ages of 6 months and 24 years old, and nonelderly adults with such underlying medical conditions as asthma, for example.

Should there be a shortage of vaccine supply, prioritizations will be made for: pregnant women, household contacts of those children under the age of 6 months, a subset of healthcare professionals who have direct contact with H1N1 patients, children between the ages of 6 months and 4 years old, and children between the ages of 5 years and 18 years with underlying complications. Those “shortage-contingency” groups number approximately 40 million patients, Schuchat said, the larger priority groups number some 159 million.

“We do think it is likely that two doses [of this vaccine will be necessary], and that’s what we’re planning,” she added. For school children also being inoculated with a seasonal vaccine, that means as many as four shots—two vaccine shots and two boosters. Some of the studies that are being carried out are looking at simultaneous administration of H1N1 and seasonal influenza vaccines versus subsequent administration. “Our assumption is it is very likely that they can be given together,” Schuchat said.

“At this point, 83% of the population is recommended to get an annual flu vaccine, and we recommend it for anyone who wants to reduce their risk of flu,” Schuchat said. “Unfortunately, only about 40% of the U.S. population received the flu vaccine last year, so we’re really recommending an intensifying use of this vaccine because it does protect against illness and complications like hospitalization and severe outcomes.”

Schuchat also stressed that healthcare workers need to get vaccinated, especially this year. “We recommend them strongly to receive the seasonal flu vaccine,” Schuchat said. “And I’m expecting when H1N1 vaccine recommendations come out, it’s very, very likely healthcare workers will be in that group that ought to get vaccines as well.” Presently, the CDC is estimating that enough novel H1N1 vaccine, if approved, may be ready by mid-October to sustain a national vaccination program.

Also muddying the waters of any projection is media coverage and consumer reaction. Extensive media coverage earlier in the season before any significant outbreaks could prompt many Americans to be extra-vigilant in preventing influenza transmission through hand-washing and the use of sanitizers, for example, cutting into the spread of infection.