"My concern is that this is speculation and will only confuse the public," said Dr. Judy Monroe, state health commissioner of Indiana. "There are other respiratory viruses that circulate all the time and unless individuals had confirmatory testing they do not know if they had the 2009 H1N1 influenza."
Dr. Karen Smith, public health officer with the Napa County Health and Human Services in Napa, Calif., said that the idea that the preliminary wave of the new flu strain could have contributed to herd immunity is an interesting one. But she said that it must be viewed cautiously.
"In general, I am very much in favor of the press discussing these sorts of issues and 'theories' as long as that discussion is complete and provides all sides of the issue," Smith said. "Unfortunately, it seems to me that the pressure to provide three-minute-or-less news stories designed to capture the interest of the audience does not lend itself to providing the kind of balanced information the public both needs and deserves."
Other public health officials shared similar concerns.
"It is definitely appropriate to point out that, despite these data, an overwhelming majority of people were not infected by this virus," said Dr. Tony Marfin, Washington state communicable disease epidemiologist. "The conditions for widespread transmission may simply not be in place in Seattle [and] Washington yet."
"I'm concerned that this could give people a false sense of security, leading some to eschew vaccination, with the consequence that they contract the flu and spread it to others," said Dr. Paul Cieslak, communicable disease program manager for the Public Health Division of the Oregon Department of Human Services. "I acknowledge the theoretical possibility that some areas of the country have had enough influenza to develop herd immunity, but the bottom line is that we don't know which areas they are."
Dr. Timothy Jones, state epidemiologist with the Tennessee State Health Department, noted, "Unfortunately, it's always dangerous to have scientific debates in the public domain, which too often seems to lead to the population -- or media -- getting the wrong message. ... It is very worrisome to me that this is all going to give the impression that 'If the flu has gone through, then I'm probably immune and don't need the vaccine.'"
And Dr. Kelly Moore, medical director of the Tennessee Department of Health's immunization program, said, "My impression is that some people are looking for any excuse to decide not to be vaccinated, and such people would seize on this as justification."
Complicating the issue is that herd immunity is not always a cut-and-dried issue. Specifically, said Michael McDonald, president of the not-for-profit global health care organization Global Health Initiatives, Inc.
"Given that the most susceptible populations and the most likely transmitters of diseases in some areas with high population density were hit harder in the first wave, it is likely that they would have less rapid transmission in the second wave, especially within specific social networks, [for example], students within a specific high school, or soldiers within a specific barracks, family members, or employees within a specific building," McDonald said.