Influenza Vaccines, Influenza Drugs - Both Losing Effectiveness

This flu season got off to an unusual start with a well-publicized study that found influenza vaccines are far less effective for the elderly than previously thought. A second study found a worldwide viral resistance to several drugs that are widely prescribed once a person comes down with the flu. Both were published this month in the British journal, The Lancet.

  The first study was a systematic review of the evidence for the effectiveness of influenza vaccines in people aged 65 years and older. Studies in this review were conducted in many countries over the course of 37 years. People living in long-term care facilities were more likely to benefit with a 42% reduction in deaths caused by influenza and pneumonia. Whereas elderly people living on their own had a more modest 30% reduction in hospitalizations for pneumonia. The review was conducted by Tom Jefferson, MD, and colleagues at the Cochrane Collaboration, an international organization that evaluates studies to determine the efficacy of medical care.

  While the reductions in deaths and hospitalizations described above appear praiseworthy, they are actually more modest than meets the eye—something that will become clear once you learn how flu vaccine studies are conducted. These reductions are also more modest than those quoted by the Centers for Disease Control and Prevention. This federal agency, known as the CDC, is the most influential promoter of flu vaccines.

  It is possible that this review by Jefferson and colleagues might initiate a more honest public discussion about the issue. And this, in turn, might lead to improvements in vaccines. Not only is the impact of vaccines oversold to the public but there is also a lot of confusion over the definition of influenza.

                                     Influenza and Influenza-like Illness

 Each flu season between 5% and 20% of the population comes down with symptoms of the illness. A vaccine, at best, will only lower the chances of getting influenza. What isn’t explained to the public is this: in any given year, the vaccine has some proven effectiveness only against influenza A or B. This is what researchers call influenza, and it afflicts fewer than 15% of all people who appear to have the flu. All other forms of the flu are called influenza-like illness. Both types cause exactly the same symptoms: headache, fever, muscle aches, cough, and runny nose. Doctors have no way of distinguishing the two types without a blood test or a culture.

 Every year, the vaccine formulation changes.  According to the CDC Web site, “three viruses (two subtypes of influenza A viruses and one influenza B virus) are selected to go into the flu vaccines for the following fall and winter. Usually, one or two of the three virus strains in the vaccine are changed each year.” The selection is based on a combination of educated guesswork, flu outbreaks in Asia, and recommendations of the World Health Organization. “This guesswork actually works quite well in healthy adults, [but] not so well in the elderly,” warned Dr. Jefferson, the lead author of the new review in an e-mail interview.

  How well a vaccine will protect you against influenza depends on the virus strains selected that year and whether it matches the circulating viruses in your environment. At the section of its Web site for health professionals, the CDC gives a high rate of effectiveness for vaccines. For example, the MMWR (Morbidity and Mortality Weekly Report) 2004, states, “When the vaccine and circulating viruses are antigenically similar [emphasis ours], the influenza vaccine prevents influenza illness among approximately 70%--90% of healthy adults under age 65 years and children one year and older 77%-90%.” Note the carefully worded qualification.

  In other words, if influenza A or B viruses are circulating in your part of the world and the vaccine happens to be the right match, then the vaccine might lower your chances of getting influenza by 90%. The vaccine, however, provides no protection if people in your immediate vicinity have influenza-like illness.

                                                        Drugs to Treat Influenza A

  The second study, published in the same issue of The Lancet, found that influenza A viruses have developed a resistance to drugs that are widely prescribed to people once they have flu-like symptoms. Rick Bright of the CDC and colleagues analyzed 7,000 blood samples of flu viruses collected from people around the world and found a resistance to Symmetrel, Flumadine, and others in a drug class called adamantine. (One of these drugs is given immediately on the presumption that the patient has influenza A because the drug must be taken within the first 48 hours of the onset of symptoms. Until recently, these drugs shortened the duration of influenza A by 30 hours.)

                                              Vaccine Review’s Puzzling Results

  The first study—the review by Jefferson and colleagues—had a puzzling finding about the vaccines’ effect on elderly people not living in nursing homes. When the reviewers combined data from 15 studies, they found that inactivated influenza vaccines were ineffective against influenza-like illnesses, influenza, or pneumonia, but prevented up to 30% of hospitalizations for pneumonia. How can vaccines be useless in preventing illness but helpful in preventing hospitalizations for pneumonia? “We are not sure,” answered Dr. Jefferson. “Our  [finding] was based on non-randomized studies, which are well known for producing overestimates of effectiveness. The real effect is likely to be more modest.”

  This qualification didn’t make it into the CDC “talking points” memo that went out to the media on the day Dr. Jefferson’s review made headlines across the country. The CDC first acknowledged, “Vaccine effectiveness is not 100%,” but then went on to uncritically assert, “The [review] did demonstrate that influenza vaccine is effective in preventing the complications and death from influenza in older persons, both in the community and in long term care facilities.

  But qualifications were present throughout the review by Jefferson and colleagues. Phrases like “with good vaccine match and high viral circulation” preceded findings of vaccine effectiveness. When asked how often the vaccine matches the viruses circulating in any given flu season, Dr. Jefferson said, “Unless there is a known epidemic underway in the surrounding community and someone is doing real time surveillance (i.e., testing of specimen), never. The problem with such studies is that they are logistically very difficult, as we acknowledge in our review.”

  As for that honest discussion about vaccines and how well they work, Dr. Jefferson identified a major stumbling block. “Vaccines are a business, like any other. The only difference is that governments are co-sponsors with industry,” he explained. “Overestimation of the threat by the target diseases, suppression of data on possible adverse events, and exaggeration of effectiveness are frequent, as the case of influenza vaccines demonstrates. In the case of population vaccination programs, both government and industry have conflicts of interest. Beware.”

Maryann Napoli, Center for Medical Consumers©, October 2005