dramatic increase in influenza activity

The CDC just published their influenza update, showing that it is now widespread in 43 states for the week ending 2/4/17 (see https://www.cdc.gov/flu/weekly/). Details:

--There are very high levels of flu activity in the South and Southeast, and most of New England (though not so much in MA, NH, VT)
--20 reported pediatric deaths so far, 5 in the last week
--21% of the samples sent to the lab have been positive for flu
--88% are influenza A, and of these 92% are subtype H3; and a subsample found it to be the same H3N2 strain which is covered by the vaccine
--none of the samples tested showed resistance to neuraminidase inhibitors (eg oseltamivir, zanamivir or peramivir), though rare international cases have shown resistance to these meds, both to H1N1 and H3N2
--hospitalization rates from flu since October 2016 have been 24.3/100K. the vast majority in these have been in those >65yo (113.5/100K), and a review of 796 cases (11.7%) found that 95% had at least one reported underlying medical condition, mostly cardiac, respiratory, metabolic disorders (esp diabetes), or neurologic disorders; with most common ones being asthma, chronic lung disease, and multiple sclerosis or muscular dystrophy
Commentary:
--there are no data in this report at the apparent effectiveness of the current vaccine (ie, were these cases of flu mostly in those not getting the vaccine??), though it is reassuring that that the match of vaccine subtypes did indeed reflect those of the current outbreak
--one concern raised a few months ago was that there may be waning immunity after vaccination. The vaccine is available earlier than before, typically at the end of the summer, with instuructions from the CDC and local health department to vaccinate people right away. But it seems that influenza outbreaks are occurring most often in the feb-april time-period. And, a study of the 2011/12 season showed that those immunized <3months before the flu outbreak had 53% vaccine effectiveness, whereas those immunized more than 3 months before had  only 12% effectiveness. (see Peabody RG. Euro Surveill. 2013 18(5):pii=20389)
--it seems reasonable to continue giving the vaccine even now  in the midst of this outbreak, though there is about a 2 week period prior to its being effective. And to consider chemoprophylaxis, especially given the susceptibility of the current subtypes (see https://www.cdc.gov/mmwr/pdf/rr/rr6001.pdf for more info on chemoprophylaxis)

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