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Be mindful of influenza, even in the spring
Since influenza reaches different places at different times, one may want to continue to immunize in some locales into early spring.
The influenza season has arrived about on schedule; that is, it seems to have peaked in most parts of the country in February (MMWR. 2008. 57(07);179-183).
As of the week ending March 8, influenza-like illness was above the seasonal threshold in eight of nine regions of the country but falling. It was still widespread in 42 states. The fact that influenza is most frequent in the month of February this year does not mean that we will not see cases for several weeks after this. In fact, the season has peaked at this time in 43% of the years. It peaked in March in 13% of years and April or May each in one of 30 seasons (For recent years, see table). Since influenza reaches different places at different times, one may want to continue to immunize in some locales into early spring.
One might ask whether one spring immunization can be counted as one of the two doses required for first-time young vaccines in the following season. The Advisory Committee on Immunization Practices would say two doses in the same season are still required for new vaccines younger than 8 years. This may be especially true as the match between vaccines and circulating strains this influenza season has been poor. As a consequence, all three of the strains in this year’s vaccine will be replaced in the 2008 to 2009 season. One can expect some but not optimal protection from the current vaccine this year.
The change in pediatric recommendations for next season, which has not received final approval, is that all individuals from 6 months up to age 18 years receive influenza vaccine annually. There is confidence that the manufacturers will be able to provide ample doses. The glitch, however, may be in the ability to produce enough mercury-free killed vaccine, as there has been a wave of reaction by parents to any mercury-containing vaccines. A non- thimerosal-containing alternative would be live-intranasal vaccine, which now can be given to children aged 2 and above. A major problem may be in the logistics of immunizing a new group of patients that are not scheduled for regular check-ups during the preferred season for immunization, the late fall, when offices tend to be quite full already. Many have proposed alternative sites, like pharmacies and supermarkets where many adults now get their immunizations.
The other cause for concern is that the neuraminidase inhibitors, which we have relied on in the absence of a vaccine against avian flu and for treatment of current circulating strains, have run into some problems.
Widespread resistance to H1N1 strains has been detected in Europe; the highest rate in Norway is more than 68% with 38% in France and about one-quarter of isolates in the Low Countries. Canada is reported to have 13% resistance to influenza A (H1N1), according to WHO estimates.
In the United States as of Feb. 23, 2008, CDC officials have reported 9.6% of H1N1 viruses tested were resistant to the antiviral drug oseltamivir (Tamiflu, Roche). Zanamivir is effective against all strains. Slightly lower resistance rates have been found for this strain for amantadine, but the other strains of influenza are highly resistant to the amantadines; thus, oseltamivir is still the drug of choice. Although H1 was predominant earlier in this influenza season, H3 now is more common in most areas. These ratios may vary regionally. In my area, Washington, D.C., H3 isolates slightly exceed H1 isolates and A is slightly more abundant than B strains. Nationally, the A type is about three times more abundant than B, and H3 is about two-and-a-half times greater than A1.
The manufacturer has posted a warning of abnormal behavior especially in teens who have been given the neuraminidase inhibitors. This was first noted in Japan.
I will end this on a personal note. I had started writing this two weeks ago when my writing was interrupted by illness characterized by cough, rhinitis, anorexia, fever and malaise.
I had taken the influenza vaccine so I can attest to the fact that it was a poor match this year. I woke up yesterday with increased fever to discover it was not 9 a.m. but 9 p.m.
I went to the emergency department as my fever had increased. I was concerned about secondary infections. After sitting there for more than two hours (so much for flu preparedness!!), I decided, as it was well past my bed time, that I would go home and try my physician in the morning. I am a firm believer in “the physician who treats him/herself has a fool for a doctor.” The next morning I had felt a bit better and rather than see my doctor, who would have undoubtedly felt the need to give me an antimicrobial, I just continued chicken soup, tea and honey and ibuprofen. Thus I did make a medical decision by not going to my doctor and not getting an antimicrobial. He is a sweetheart but I cannot help but feel that other physicians who care for me feel under some pressure to “do something.” I did not get there soon enough for oseltamivir to have made a difference, and in my part of the country rimantadine might have been as good a choice because of the presence of H1 strains at this time.
It has turned out to be a restful week, and I probably have dropped a couple of pounds. It was nice to listen to music a bit more closely, look out at the blossoming trees and enjoy the love of friends and family. It certainly has reinforced my respect for influenza.