September 26, 2009 — The good news is that the vaccine against influenza A (H1N1) will be available by the middle of October, that more people are getting immunized against influenza than in the past, and that the virus's genetic make-up is not changing.
The genetic stability means that the vaccine is highly likely to be effective, said Thomas R. Frieden, MD, MPH. Dr. Frieden, the director of the Centers for Disease Control and Prevention, spoke yesterday at a press briefing.
In addition, the newly approved vaccines against H1N1 influenza appear to be effective after a single dose in people aged 10 years and older.
Commonsense hygiene practices are also critical to preventing the virus from spreading, he said. Physicians should tell patients or their children to defer returning to work or school until 24 hours after body temperature has returned to normal without fever-reducing medication, and all people should cover coughs and wash hands frequently, he said. People who do get influenza should be treated promptly with antiviral medication only if they are at risk for complications or if they become severely ill, such as with shortness of breath or a high fever. Antiviral medication must be initiated within 48 hours of the onset of influenza to be maximally effective, he said.
Dr. Frieden summed up the known and unknown issues to date regarding H1N1. For example, it is known that H1N1 influenza seems to be a moderate disease, and therefore no more severe than the strains of influenza typically seen; the pattern of affecting primarily children and young adults is holding; and its prevalence seems to be on a downward trend.
However, as with all strains of influenza, unforeseen curves and bumps in the road are the rule, not the exception. "Influenza is the most unpredictable of contagious diseases," he said. What is unknown about H1N1 illustrates this point. For example, it is not known whether the trend downward indicates that H1N1 will retreat permanently or whether it will return. Similarly, epidemiologists do not know whether another flu season will occur, in this case driven by H3 influenza, the more common strain in circulation this year.
The widely spreading misinformation is one of the known factors that is a barrier to adequate immunization, Dr. Frieden said. "Misinformation spreads more rapidly than influenza," he added. Physicians need to clarify misconceptions that are alarming and those that promote complacency. For example, physicians should stress to their patients that it is impossible to get influenza from the vaccine because it is based on a killed virus. Conversely, patients should be steered away from the complacency-inspiring misconception that influenza is not a severe illness, and therefore vaccinations are unnecessary.
There are also daunting logistical barriers to getting the vaccine out of the manufacturing plants, onto refrigerated trucks, and out to the 90,000-plus facilities that administer the vaccine to patients. Therefore, even though everyone who should get the vaccine should have had the opportunity by mid- to late October, there may be a temporary shortage earlier in the month until the distribution is complete. Those who should get the H1N1 vaccine sooner are people who are at risk for complications, such as those with underlying chronic health conditions, caregivers of such patients, those who live with them, and people who live or work with infants younger than 6 months, who are not able to tolerate the vaccine.
