Flu vaccination can sometimes seem like a national obsession—after all, viral disease–fighting options are scant. But is it a rational obsession? According to the Centers for Disease Control and Prevention, despite rising vaccination rates, the estimated number of annual flu-related deaths has varied widely from 1976 through 2007, ranging from as low as 3,000 to as high as 49,000.
There's much that we still don't know about vaccine effectiveness, but one reason for this variability in numbers of flu-related deaths is the quality of the antigenic match between annual vaccine strains and actual circulating strains. In well-matched years, the optimal effectiveness of the flu vaccine is around 70% to 90% for young, healthy adults and children, lower for the elderly and immunocompromised. In mismatched years, though, the effectiveness rate can be considerably lower. Antigenic drift, for example, occurs when there is an unexpected mutation in the surface antigen of the virus, potentially leading to a mismatch with the vaccine strains and a significant reduction in vaccine effectiveness.
Yet in years in which the vaccine has not closely matched the circulating virus strains, the mortality rate has often remained relatively stable. And consider the paradox that despite increasing flu vaccination rates among the elderly, mortality from influenza and pneumonia is rising, not falling, in that population. While there may be other factors at play, such as that healthy elderly people are more likely to get flu shots than unhealthy elderly people, the point here is that the flu vaccine is not a magic bullet.
Vaccines are simply one available tool in a multidimensional war. The probability that a healthy person will contract influenza is confounded by a number of factors, including the number of exposures, method of transmission, organism strain, and the person's inherent immunity to a particular strain. Vaccination compliance alone shouldn't be viewed as the single most important influence on mortality rates. Overreliance on mandatory vaccination programs, even if they are relatively effective, can obscure other important preventive issues that need addressing.
Despite ethical concerns over the compulsory vaccination of health care workers, mandatory programs appear to be the wave of the future. In 2009, after the influenza A (H1N1) virus was declared a pandemic, New York became the first state to mandate flu vaccination of health care workers. A judge temporarily halted the seasonal mandatory program after several nurses brought suit and nursing unions and organizations argued that mandatory vaccination violated civil liberties; subsequently, the New York State mandate was suspended owing to a shortage of H1N1 vaccine.
In 2011, a North Carolina hospital implemented mandatory vaccination as a condition of employment, forcing employees who declined the vaccine to wear a mask at all times. The unintended consequence was that clerical workers with no patient contact were forced to wear masks even if alone in an office. In 2012, the rule was therefore relaxed, and employees were only required to wear masks within six feet of a patient.
Clearly, these mandatory programs are evolving. The hope is that they will affect overall flu mortality, not simply improve vaccination compliance rates.
The future of viral treatment is promising. For example, researchers at the Massachusetts Institute of Technology recently discovered a method to induce infected cells to destroy themselves before a virus can spread. While there's hope for a magic bullet, at present flu vaccinations must be utilized in the proper context. Vaccination programs should neither allow a false sense of security nor permit equally important preventive measures, such as effective handwashing, surface disinfectants, and isolation procedures, to be casually dismissed.
A comprehensive approach is a rational approach. Viral disease in general, and influenza in particular, has too much pandemic potential to take for granted.