Surveillance for laboratory-confirmed influenza-associated pediatric deaths since 2004 has shown that most deaths occur in unvaccinated children. We assessed whether influenza vaccination reduced the risk of influenza-associated death in children and adolescents.
We conducted a case–cohort analysis comparing vaccination uptake among laboratory-confirmed influenza-associated pediatric deaths with estimated vaccination coverage among pediatric cohorts in the United States. Case vaccination and high-risk status were determined by case investigation. Influenza vaccination coverage estimates were obtained from national survey data or a national insurance claims database. We estimated odds ratios from logistic regression comparing odds of vaccination among cases with odds of vaccination in comparison cohorts. We used Bayesian methods to compute 95% credible intervals (CIs) for vaccine effectiveness (VE), calculated as (1 − odds ratio) × 100.
From July 2010 through June 2014, 358 laboratory-confirmed influenza-associated pediatric deaths were reported among children aged 6 months through 17 years. Vaccination status was determined for 291 deaths; 75 (26%) received vaccine before illness onset. Average vaccination coverage in survey cohorts was 48%. Overall VE against death was 65% (95% CI, 54% to 74%). Among 153 deaths in children with underlying high-risk medical conditions, 47 (31%) were vaccinated. VE among children with high-risk conditions was 51% (95% CI, 31% to 67%), compared with 65% (95% CI, 47% to 78%) among children without high-risk conditions.
Influenza vaccination was associated with reduced risk of laboratory-confirmed influenza-associated pediatric death. Increasing influenza vaccination could prevent influenza-associated deaths among children and adolescents.
Comments
RE: Influenza Vaccine Effectiveness Varies
The recent CDC analysis comparing pediatric influenza-associated deaths with various control cohorts, found vaccination to be effective in preventing significant numbers of such deaths.[1] Their conclusions were based on lumping together various ethnicities, ages, vaccine types and influenza seasons. More could be learned by teasing those factors apart. Unfortunately, vaccine type was known for a small number (62) of deaths whose vaccine status was known (291). Until the last (2013-2014) season in the study, the live attenuated influenza vaccine (LAIV) was more effective than the inactivated form which is almost exclusively used for high-risk patients. Thus, if the 81% (50/62) of known vaccine type being the inactivated form was representative of all vaccinated influenza-associated pediatric deaths, the preponderant use of the less effective inactivated vaccine could explain why vaccine efficacy (VE) was lower in high-risk patients than in non-high-risk patients. That could also explain why VE in high-risk children was only 38% in the heaviest season (2012-2013) and up to 75% in the 2013-2014 season when the inactivated vaccine outperformed LAIV. Supporting that concept is the fact that VE was high (63-89%) for the non-high-risk group (which would use much more LAIV) in the first three seasons, but only 48% in the 2013-2014 season after CDC had actually expressed an LAIV preference. LAIV did so poorly in the 2013-2014 season (when it became quadrivalent) and in the next two seasons, that CDC essentially took it off the market in 2016. It is very possible that adding a fourth strain could have caused interference in recipients of LAIV, as it works by causing a mucosal infection. That may be the main reason why its efficacy fell. Perhaps more pediatric influenza-associated deaths could be averted if LAIV went back to 3 strains and was approved for high-risk patients.
Other differences occurred by age groups; VE 61-76% for 6 months to 12 year ages vs. 40% in 13-17 year-olds (or 33% in older high-risk patients). Yet VE was 60% in 13-17 year-olds without high risk conditions. That may be also due to a disproportionately higher use of LAIV in non-high-risk patients. Other than in the last season, the protection afforded by vaccination may have been largely from the LAIV.
Only 8% (3/39) of blacks who died with influenza were vaccinated which was significantly lower than in whites who died with influenza. That correlates with a significantly overall lower rate of vaccination in blacks than in whites. [2,3] The proportion of deaths in blacks of known vaccination status (39/291 or 13%) was slightly lower than the proportion (15%) of US blacks aged < 18 years in the years studied. Blacks may have lower vaccine rates because as a group they are more resistant to influenza. [3] Blacks who do not have innate resistance to influenza may still resist vaccination because their relatives and friends don’t see the benefit of it. Patients who have had influenza infections before are at highest risk for future influenza infections and should be especially targeted for vaccination. [3]
References
1. Flannery B, Reynolds SB, Blanton L, et al. Influenza vaccine effectiveness against pediatric deaths: 2010-2014. Pediatrics. May 2017;139(5)e20164244;DOI:10.1542/peds.2016-4244
2. Schuller KA, Probst JC. Factors associated with influenza vaccination among US children in 2008. J Infect Public Health 2013;6:80-8.
3. Field SS. Reasons for influenza vaccination underutilization: a case-control study. Am J Infect Control. 2016 Oct 1;44(10):1084-1088. DOI: 10.1016/j.ajic.2016.05.021
Concerned Citizen
Such proclamations should be viewed with skepticism without more open access to who has backed and orchestrated the research. After reading a great deal of research demonstrating doctors being paid by pharmaceutical companies to lecture on the efficacy of their drugs, and doctors receiving bonus's of sorts for prescribing pharmaceuticals, and insurance companies determining the time each doctor can spend with their patient (often as little as 15 minutes) it is only logical to recognize that a good deal of research is biased and backed by their own industry. I've seen copious research on vaccinations that have caused or appear to have irrefutable evidence linking them with subsequent serious illness in children and adults. Vaccination is an important medical issue that warrants serious neutral research with verifiable documentation that begins with ties the researchers and universities have. I imagine there are beneficial and harmful vaccines. Blanket acceptance of vaccines is as unwise as blanket refusal of vaccines.