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Immunization is the best defense against influenza
It is important to include yourself and your office staff among those to be protected.
Will this be the year of a major influenza epidemic?
I do not know and anyone who says they do should be suspect. But, we need to prepare for the influenza season whatever it turns out to be. What control measures beyond immunization are important and what will be the role of antivirals? Who should be immunized and with what and when?
The “when” question is easy to answer. Now! This is especially important for those people younger than 8 years of age who have not received two doses in a single season previously (MMWR.2007;56(RR06):1-56). They will require two doses this season.
It is important to remember that those who are not immunized in the fall should be immunized into the coming year as for the past several years the epidemic has peaked in February. No shortage of vaccine is anticipated this year.
It is important to include yourself and your office staff among those to be protected. It is likely that these people will be exposed. They should not fall ill, lose time from work, spread the disease to patients or to members of their own families. There is a theoretical risk of transmission of live vaccine virus to patients who are immunocompromised and this may govern the choice of vaccine for health care providers. To decrease the risk of those children younger than 60 months of age being exposed, their household contacts also should be immunized. This would include school-aged siblings. It is also suggested that vaccine be offered to all children whose parents want to diminish their chances of getting influenza.
Information on the vaccines for children can be accessed at www.cdc.gov/vaccines/programs/vfc/default.htm. The recommendations to immunize high-risk individuals with inactivated vaccine, including those with asthma, remain the same (MMWR.2007;56(RR06):1-56).
The intranasal live vaccine (FluMist, MedImmune) has been approved for those as young as 2 years of age. Doses of .1 ml in each nostril can be given four rather than six weeks apart and the vaccine can be stored at refrigerator temperatures (MMWR.2007;56(38):1001-1004). Which one to use? Children 6 to 24 months can receive only inactivated vaccine. From 2007 to 2008, both live and killed vaccines will contain a different A-H1N1 component, A/ Solomon Islands/3/2006 H1N1-like strain.
Why should one consider switching from the inactivated to the live for those older than 24 months or age? The most obvious reason is that it avoids another intramuscular injection in a schedule that already is saturated. There may be other reasons as well. In the initial clinical trials, the intranasal vaccine seemed to provide longer protection against somewhat divergent strains if the vaccine strain did not match the circulating strain (NEJM. 2007;356:685). In a recently published study comparing the live and killed vaccines in individuals between 6 and 60 months of age, the attack rate of virologically proven cases was 54.9% lower in the recipients of the live vaccine (NEJM. 2007; 356:685-696). The differences were greatest for influenza A/H1N1, a mismatched strain, where there were 89.2% fewer cases with the live vaccine. There also were fewer cases of otitis and lower respiratory disease. The adverse effects were not significantly different in those children older than 24 months for which the vaccine is approved. Children with a history of severe asthma or wheezing within 42 days prior to enrollment were excluded from the study.
People who have a history of “hives or swelling of the lips or tongue, or who have experienced acute respiratory distress or collapse after eating eggs” are potentially at risk if they are immunized with either of the current vaccines as these, in contrast to other routinely administered vaccines, are propagated in embryonated eggs. For those parents who are concerned about the traces of mercury in some influenza vaccines, the Sanofi Pasteur single-dose vials for children and the live-attenuated vaccines are free of mercury.
The downside of the live vaccine is its greater cost and the fact that some may find the new method of giving the vaccine more troublesome than just giving an injection. Although it can be given at the same visit as other vaccines, other live vaccines that are not given at this time should be separated by a month. As this is a live vaccine, it should not be given to severely immunocompromised people or to children with asthma or with recurrent wheezing. Finally, the intranasal vaccine should be postponed in children with an obviously snotty nose, as the vaccine may not reach the mucosa.
The neuraminidase inhibitors, rather than amantadine or rimantidine, now are the choices for antiviral therapy for influenza as resistance to the latter has become significant. They should be used within 48 hours after the onset of symptoms if they are to be effective. They can be expected to decrease the length of illness by about 36 hours. The effect of oseltamivir is said to be apparent within 24 hours and there has been reduced the use of antipyretics (Pediatr Infect Dis J. 2001;20:127). There may be a particular advantage to treatment of children with asthma. Thus far, resistance has been minimal. The most common adverse event in children has been vomiting. Of concern is a report from Japan of significant central nervous system effects in some children. There are new dosage forms of oseltamavir of 30 and 45 mg capsules. The drug is licensed for children over a year and a liquid form is available.
Neuraminidase inhibitors also have been used successfully as prophylaxis. There are approved CLIA-waived rapid tests for specific diagnosis of influenza, which although fairly accurate do suffer from some specificity and sensitivity issues. Although the greatest value of these tests would appear to be early in the influenza season, it is important to realize that these tests will have a lower positive predictive index when there is a low incidence of disease, thus it may just be a valuable reminder of “what’s going around.”
One should familiarize oneself with the plans for your community in the event of a pandemic of a new strain of influenza virus. In any influenza epidemic if is prudent to inculcate procedure to decrease the likelihood of spread.
Highly recommended is www.cdc.gov/flu/professionals/infectioncontrol/resphygiene.htm, which contains instructions for patients and health care professionals on such practices as tissue disposal, covering your mouth while coughing, hand washing and when masks are appropriate. Most important, get immunized!