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Will the Nasal Flu Vaccine Be Making a Comeback?

APR 26, 2017 | EINAV KEET
With now only 10 states reporting widespread flu activity, a recently released study examines how the delivery methods of the influenza vaccine can be optimized.

In the FluView report for the week ending April 15, the Centers for Disease Control and Prevention (CDC) is reporting that, for the first time in 2017, the proportion of outpatient visits for influenza-like illness in the United States is now below the national baseline of 2.2%. In addition, fewer states are reporting widespread and regional flu activity, and the number of flu-positive respiratory specimens reported by public health and clinical laboratories has fallen from 3,044 in the previous week to 2,249 in the most recent week. The CDC notes that it expects sporadic flu activity to continue for several weeks, as flu season continues to be dominated by influenza B viruses, which now account for 69% of the viruses reported by public health laboratories in the United States.

This season, the CDC estimates that the flu vaccine’s effectiveness reduced the risk of infection by about 48%. So far for the 2016-2017 season, the flu shot has been 43% effective against influenza A H3N2 viruses and 73% effective against influenza B viruses. In 2016, the CDC’s Advisory Committee on Immunization Practices voted against offering the live attenuated influenza vaccine (LAIV) – the inhaled “nasal spray” delivery method of the vaccine – for the 2016-2017 flu season, due to its low efficacy rates. However, a new study published in the American Journal of Preventive Medicine suggests that there may still be a place for the inhaled vaccine.

In the recent study, University of Pittsburgh researchers noted that despite its lower efficacy rates, eliminating the nasal influenza vaccine has resulted in a reduced overall rate of flu vaccine uptake in the United States. Thus, eliminating this form of vaccination may lead to more flu-related illnesses. “The CDC is being appropriately cautious and doing the right thing based on available data,” said lead author Kenneth J. Smith, MD, MS, in a recent press release pertaining to the CDC’s decision to stop offering the nasal spray flu vaccine. The study points out that the LAIV continues to be effective and available in other countries, though the authors aren’t sure why. In the United States, 20.9% of children between the ages of 2 and 8 become infected with the flu when the flu vaccine is only available in the form of a shot, compared with 23.5% if both the needle and nasal vaccines are offered. Dr. Smith points out that if the nasal vaccine is effective in preventing flu in more than 63% of recipients, then health officials will be able to support the availability of both forms of vaccination.

“Our study finds that it would take only relatively small changes to tip the scales back in favor of offering the LAIV, so close monitoring is very important,” he said. In addition, the Pittsburgh Vaccination Research Group, which tracks flu vaccine uptake, will continue to monitor flu cases and vaccination rates and correlation between the two, in order to help “guide flu immunization recommendations,” said Richard K. Zimmerman, MD, MPH, senior author of the study, and professor at the Pitt School of Medicine, Department of Family Medicine, and at the Pitt Graduate School of Public Health, Department of Behavioral and Community Health Sciences.
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Influenza A (H3N2) has caused most of the illnesses in this severe flu season, but influenza B is becoming increasingly responsible for more infections as the flu season continues to hit the United States.