Influenza vaccine effectiveness

Holly, Andrew, and I have been settling in to our new home. Holly has done an amazing job of setting up her new piano studio. I've been brushing up on my (non-existent) handyman skills around our 120 year old house.



Andrew's room in our old house was too small to play on the floor



It's time for a trim when Andrew can grab a handful of beard

 

Flu vaccine recommendation for children 6 months to 8 years of age

I took Andrew in for his second flu shot this week. He received his first dose of flu vaccine at his 6 month well-child visit last month. The current Advisory Committee on Immunization Practices (ACIP) flu vaccine recommendation is two doses of 2012-2013 flu vaccine at least one month apart for children 6 months to 8 years of age who have not received at least two doses of flu vaccine since July 1, 2010 and one dose of 2012-2013 flu vaccine for children who have received at least two doses of flu vaccine since July 1, 2010.

Confused? The ACIP included this algorithm in their recommendations:

Influenza vaccine effectiveness

The words efficacy and effectiveness have different but related meanings in medical literature. Basically, efficacy is how well an intervention works in clinical trials and effectiveness is how well the intervention works in the real world. The efficacy and effectiveness of vaccines are both calculated by comparing the number vaccinated and unvaccinated people who develop the disease after being vaccinated.

In January the Centers for Disease Control and Prevention (CDC) published early estimates of seasonal influenza vaccine effectiveness. In that report, the overall vaccine effectiveness (VE) was:

Influenza A and B:    62% 

Influenza A:             55%
Influenza B:             70%

This week the CDC published interim adjusted estimates of seasonal influenza vaccine effectiveness. They found similar levels of protection against influenza in people ages 6 months to 64 years, but the effectiveness for people 65 years of age and older was not statistically significant; that is, the data they collected did not demonstrate that flu vaccine protects older adults from influenza.

Influenza A & B			H3N2 (Influenza A)			Influenza B
Age	VE		Age	VE		Age	VE
6 mos–17 years	64%		6 mos–17 years	58%		6 mos–17 years	64%
18–49	52%		18–49	46%		18–49	68%
50–64	63%		50–64	50%		50–64	75%
≥65	27% (n.s.)		≥65	9% (n.s.)		≥65	67% (n.s.)
Overall	56%		Overall	47%		Overall	67%

Last year the Center for Infectious Disease Research & Policy (CIDRAP) published a report titled The Compelling Need for Game-Changing Influenza Vaccines. The report includes an analysis of flu vaccine efficacy and effectiveness that was published in Lancet Infectious Diseases in 2011. The CIDRAP report is an excellent review of influenza and flu vaccines. The authors discuss how current influenza vaccines target the hemagglutinin head of flu viruses, which is coded by genes that mutate almost continuously. These mutations change the shape of the hemagglutinin and reduce the ability of antibodies from immunization or previous infections to bind to the virus. This is one of the reasons flu vaccines change from year to year.

The authors of the CIDRAP report call for research and development of "universal" flu vaccines that target conserved viral antigens; that is, vaccines that target parts of the virus that are common across influenza virus types and strains. Research for universal flu vaccines is ongoing, but development is likely to take another 5 to 10 years.

In the mean time, the authors of these reports remind us that flu vaccines remain the best way to prevent influenza and its complications.

Immunizing children to protect older adults

Because they interact with children from other households as well as adults in their own homes, schoolchildren can facilitate disease transmission within a community. Previous studies have suggested that vaccinating children can protect unvaccinated people by preventing the spread of the disease from child-to-child and then to other households.

During the 2008-2009 flu season, Mark Loeb and colleagues gave flu vaccine to children in randomly selected Hutterite communities in Canada and, as a control, hepatitis A vaccine to children in other Hutterite communities. The researchers found that in the communities in which children had been given flu vaccine, the vaccine was 61% effective in preventing flu in adults who had not received the vaccine.

Because there were few adults ages 65 years and older in the communities Loeb et al. could not conclude that flu vaccine given to children can protect people in that age group. Nevertheless, the Hutterite study provided strong evidence that flu vaccine administered to children can prevent flu in unimmunized adults.

For most people, flu vaccines are moderately effective at preventing influenza. It's important to remember that, for most people, flu vaccines reduce the risk of getting the flu. That means that people who receive a seasonal flu vaccine are less likely to miss work and less likely to give the flu to someone else. Parents of vaccinated children are less likely to miss work staying home to take care of a sick child.

References:

 
Centers for Disease Control and Prevention. (2012). Prevention and Control of Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP) — United States, 2012–13 Influenza Season. Morbidity and Mortality Weekly Report, 61(32), 613-618. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6132a3.htm.

Centers for Disease Control and Prevention. (2013). Early Estimates of Seasonal Influenza Vaccine Effectiveness — United States, January 2013. Morbidity and Mortality Weekly Report, 62(2), 32-35. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6202a4.htm.

Centers for Disease Control and Prevention. (2013). Interim Adjusted Estimates of Seasonal Influenza Vaccine Effectiveness — United States, February 2013. Morbidity and Mortality Weekly Report, 62(7), 119-123. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6207a2.htm.

Centers for Disease Control and Prevention. (2013). Updated Recommendations for Use of Tetanus Toxoid, Reduced Diphtheria Toxoid, and Acellular Pertussis Vaccine (Tdap) in Pregnant Women — Advisory Committee on Immunization Practices (ACIP), 2012. Morbidity and Mortality Weekly Report, 62(7), 131-135. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6207a4.htm.

Dushoff, J., Plotkin, J. B., Viboud, C., Simonsen, L., Miller, M., Loeb, M. et al. (2007). Vaccinating to protect a vulnerable subpopulation. PLoS Medicine, 4(5), e174. http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.0040174.

Jordan, R., Connock, M., Albon, E., Fry-Smith, A., Olowokure, B., Hawker, J. et al. (2006). Universal vaccination of children against influenza: Are there indirect benefits to the community? A systematic review of the literature. Vaccine, 24(8), 1047-1062. http://www.ncbi.nlm.nih.gov/pubmed/16298026.

Loeb, M., Russell, M. L., Moss, L., Fonseca, K., Fox, J., Earn, D. J. D. et al. (2010). Effect of influenza vaccination of children on infectious rates in Hutterite communities. Journal of the American Medical Association, 303(10), 943-950. http://jama.jamanetwork.com/article.aspx?articleid=185509.

Osterholm, M. T., Kelley, N. S., Manske, J. M., Ballering, K. S., Leighton, T. R., & Moore, K. A. (2012). The compelling need for game-changing influenza vaccines: an analysis of the influenza vaccine enterprise and recommendations for the future. Minneapolis: Center for Infectious Disease Research & Policy. http://www.cidrap.umn.edu/cidrap/files/80/ccivi%20report.pdf.

Osterholm, M. T., Kelley, N. S., Sommer, A., & Belongia, E. A. (2011). Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis. Lancet Infectious Diseases, 12(1), 36-44. http://www.thelancet.com/journals/laninf/article/PIIS1473-3099(11)70295-X/abstract.

Roos, R. (2013). FDA expert: universal flu vaccine still 5-10 years off. CIDRAP News. http://www.cidrap.umn.edu/cidrap/content/influenza/general/news/feb1313hearing.html.

 

Weycker, D., Edelsberg, J., Halloran, M. E,. Longini, I. M., Nizam, A., Ciuryla, V. et al. (2005). Population-wide benefits of routine vaccination of children against influenza. Vaccine, 23(10), 1284-1293. http://www.ncbi.nlm.nih.gov/pubmed/15652671.