“If you’ve seen one flu season, you’ve seen one flu season”. Those words certainly ring true for the upcoming 2016-17 influenza vaccination season.
CDC conducts vaccine effectiveness studies each year to determine the effectiveness of the current year’s influenza vaccine. The data showed that the effectiveness against any flu virus in children 2 through 17 years of age was 3% for FluMist versus 63% for inactivated influenza vaccine (IIV).
FluMist is a live attenuated influenza vaccine (LAIV); attenuated meaning that the live virus is weakened so that it cannot cause illness. AstraZeneca is the parent company of MedImmune, the manufacturer of FluMist.
The Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC) voted at their June meeting and provided the following recommendation on the use of FluMist Quadrivalent Live Attenuated Influenza Vaccine (FluMist Quadrivalent) in the US for the 2016-2017 influenza season: since the nasal spray was so ineffective, it should not be used by anyone during the 2016-17 flu season.
2 years ago, ACIP made the unprecedented decision to make a preferential recommendation for FluMist vaccine for children 2 – 8 years of age based on previous evidence of efficacy in that age group. So what happened?
That’s what researchers are trying to understand. The answer is not clear at the current time, but there are several hypotheses.
- Suboptimal performance of the H1N1 component
- Possible interference of the viruses when they added the additional B strain to make the quadrivalent vaccine – researchers noted the decrease in effectiveness during the past 3 flu seasons, which coincides with the change to quadrivalent FluMist
- Reduced immunogenicity of LAIV because children are more highly vaccinated now
Previous data showed that FluMist was more effective in children than adults. Since FluMist has been readily available in this country for years, many children have received FluMist during that time. In other countries where FluMist was not readily available or accepted, the vaccine effectiveness data was better. This supports the theory in the last bullet – that children may not be responding as well to the vaccine after increased exposure.
While researchers have their hands full trying to determine the cause of the decreased effectiveness, the ACIP vote highlights the importance of measuring and evaluating the effectiveness of public health interventions. ACIP continues to recommend annual flu vaccination, with either the inactivated influenza vaccine (IIV) or recombinant influenza vaccine (RIV), for everyone 6 months and older.
Clinics that have not already done so, should order injectable influenza vaccine to replace any doses of FluMist that they had ordered.
Sandy Weinberg, RN BSN MA
Certificate in Travel Health™