The United States is having an early flu season with most of the country now experiencing high levels of influenza-like-illness (ILI) (reported to you in the Dec. 31 Scalpel Weekly News). There are localized shortages of the influenza vaccine. Most of the more than 130 million doses that were produced by the vaccine manufacturers this year have already been given. People who want to be vaccinated should call their provider ahead of time and may have to check in several places to find the vaccine.
Preliminary studies show the overall vaccine effectiveness is 62 percent. That means that if you have gotten the flu vaccine, you are 62 percent less likely to need to go to your doctor to get treated for flu. This is comparable to the effectiveness of flu vaccines in recent years.
About 90 percent of all of the strains circulating are included in the vaccine. Current flu vaccines only have space for three strains, two influenza As and one influenza B. The three most common strains currently circulating are the three strains in this year’s vaccine. So the pick of vaccine strains was as good as it could have been this year. The other 10 percent of strains circulating are a second influenza B. There is no evidence that the second influenza B strain is more or less severe than the other strains. Within a year or two, the CDC expects manufacturers to have on the market vaccines that have space for four different vaccines including two influenza B’s.
Since October 1, 2012, the CDC has antigenically characterized 521 influenza viruses, including 17 2009 influenza A (H1N1) viruses, 327 influenza A (H3N2) viruses and 177 influenza B viruses. All 17 of the 2009 influenza A (H1N1) viruses were characterized as A/California/7/2009-like. This is the influenza A (H1N1) component of the Northern Hemisphere vaccine for the 2012-2013 season. Of the 327 influenza A (H3N2) viruses, 325 (99%) were characterized as A/Victoria/361/2011-like. This is the influenza A (H3N2) component of the Northern Hemisphere influenza vaccine for the 2012-2013 season. Approximately 67% of the 177 influenza B viruses belonged to the B/Yamagata lineage of viruses, and were characterized as B/Wisconsin/1/2010-like, the influenza B component for the 2012-2013 Northern Hemisphere influenza vaccine. The remaining 33% of the tested influenza B viruses belonged to the B/Victoria lineage of viruses.
There are localized shortages of the pediatric suspension (liquid) of Oseltamivir Phosphate (Tamiflu), due to increased demand for the drug. The manufacturer, Genentech, has Tamiflu for Oral Suspension on intermittent backorder, however supplies remain in distribution at wholesalers and pharmacies. Tamiflu 30 mg, 45 mg and 75 mg capsules remain available. Pediatric patients over one year of age can be dosed correctly using the 30 mg and 45 mg capsules. The FDA has instructions for pharmacists on how to compound an oral suspension from Tamiflu 75 mg (adult) capsules. These instructions provide for an alternative oral suspension when a commercially manufactured oral suspension formulation is not readily available. There also are pediatric doses of Tamiflu capsules that can be mixed with a thick sweetened liquid and swallowed that way. Providers should keep this in mind when writing prescriptions for pediatric patients and advise parents that they may need to call several pharmacies to locate suspension or pediatric capsules, or they may need to identify a pharmacy that can compound in order to fill their child’s prescription.
Since October 1, 2012, the CDC has tested 70 2009 influenza A (H1N1), 600 influenza A (H3N2), and 230 influenza B virus isolates for resistance to neuraminidase inhibitors this season. The tested viruses showed susceptibility to the antiviral drugs oseltamivir and zanamivir. High levels of resistance to the adamantanes (amantadine and rimantadine) persist among 2009 influenza A (H1N1) and A (H3N2) viruses. Adamantanes are not effective against influenza B viruses.
Since the end of December, some key flu activity indicators have continued to rise, while others have fallen. Some regions may have peaked, while other parts of the country, particularly in the west, are still on the upswing. Influenza activity ebbs and flows during flu season and tends to spread across the country. It also has some variability even within states and communities. Because of the holiday season, trends are harder to predict. Nationally, it is likely that influenza will continue for several more weeks. During the past decades, the flu season has lasted an average of about twelve consecutive weeks.
The proportion of people seeing their health care provider for influenza-like illness (ILI) decreased from 6.0% to 4.3% for the week ending in January 5, but remains above the national baseline for the fifth consecutive week.
Twenty-four states and New York City are now reporting high ILI activity. Last week 29 states reported high ILI activity. Additionally, 16 are reporting moderate levels of ILI activity; an increase from 9 states in the prior week. States reporting high ILI activity for the week ending January 5, 2013 include Alabama, Colorado, Delaware, Georgia, Illinois, Iowa, Kansas, Louisiana, Michigan, Minnesota, Mississippi, Missouri, New Jersey, New Mexico, North Carolina, North Dakota, Oklahoma, Pennsylvania, Rhode Island, Tennessee, Texas, Utah, Virginia, and West Virginia.
Forty-seven states reported widespread geographic influenza activity for the week between December 30, 2012 and January 5, 2013. This is an increase from 41 states in the previous week. Widespread means that more than 50 percent of a geographic sub region in a state – like counties for instance -- are experiencing flu. Geographic spread data are based on assessments made by each state health department and show how many areas within a state or territory are seeing flu activity. The assessments made by each state health department are based on the detection of outbreaks of flu, increases in the percent of people visiting the doctor with flu-like symptoms, and patients with laboratory-confirmed influenza.
Since October 1, 2012, 3,710 laboratory-confirmed influenza-associated hospitalizations have been reported. This translates to a rate of 13.3 influenza-associated hospitalizations per 100,000 people in the United States. Influenza-associated hospitalizations are highest among people 65 and older. Of the 3,710 influenza-associated hospitalizations that have been reported this season, 46% have been among people 65 and older. Hospitalization data are collected from 15 states to calculate a rate of laboratory-confirmed influenza-associated hospitalizations that is reasonably representative of the nation. These data do not reflect the actual total number of influenza-associated hospitalizations in the United States.
The proportion of deaths attributed to pneumonia and influenza (P&I) based on the 122 Cities Mortality Reporting System is now slightly above the epidemic threshold for the first time this season. Two influenza-related pediatric deaths were reported during the week between December 30 and January 5. One of the deaths was associated with an influenza A (H3) virus, and one was associated with an influenza A virus of unknown subtype. This brings the total number of influenza-associated pediatric deaths reported to the CDC for 2012-2013 to 20.
Nationally, the percentage of respiratory specimens testing positive for influenza in the United States during the week ending January 5, 2012 decreased from 35.2% in the previous week to 32.8%. Influenza A (H3N2), 2009 influenza A (H1N1), and influenza B viruses have all been identified in the U.S. this season. During the week ending January 5, 2013, 3,369 of the 4,222 influenza positive tests reported to the CDC were influenza A and 853 were influenza B viruses. Of the 1,586 influenza A viruses that were subtyped, 98% were H3 viruses and 2% were 2009 H1N1 viruses.
See the CDC Situation Update
See the CDC Telebriefing Transcript
See the CDC’s Guidance for Pediatricians
See the FDA Drug Shortages regarding Oseltamivir Phosphate (Tamiflu)