Evidence that Vaccines in children are ineffective and/or unproven for safety.

Comment in:

Evid Based Med. 2006 Oct;11(5):140.

Evid Based Nurs. 2006 Oct;9(4):107.

Update in:

Cochrane Database Syst Rev. 2008;(2):CD004879.

Vaccines for preventing influenza in healthy children.

Oxford University, Institute of Health Sciences, Old Road Headington, Oxford, UK, OX3 7LF. sue.smith@public-health.oxford.ac.uk

BACKGROUND: In children and adults the consequences of influenza are mainly absences from school and work, however the risk of complications is greatest in children and people over 65 years old. OBJECTIVES: To appraise all comparative studies evaluating the effects of influenza vaccines in healthy children; assess vaccine efficacy (prevention of confirmed influenza) and effectiveness (prevention of influenza-like illness) and document adverse events associated with receiving influenza vaccines. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2005); OLD MEDLINE (1966 to 1969); MEDLINE (1969 to December 2004); EMBASE (1974 to December 2004); Biological Abstracts (1969 to December 2004); and Science Citation Index (1974 to December 2004). We wrote to vaccine manufacturers and a number of corresponding authors of studies in the review. SELECTION CRITERIA: Any randomised controlled trials (RCTs), cohort and case-control studies of any influenza vaccine in healthy children under 16 years old. DATA COLLECTION AND ANALYSIS: Two authors independently assessed trial quality and extracted data. MAIN RESULTS: Fifty-one studies involving 263,987 children were included. Seventeen papers were translated from Russian. Fourteen RCTs and 11 cohort studies were included in the analysis of vaccine efficacy and effectiveness. From RCTs, live vaccines showed an efficacy of 79% (95% confidence interval (CI) 48% to 92%) and an effectiveness of 33% (95% CI 28% to 38%) in children older than two years compared with placebo or no intervention. Inactivated vaccines had a lower efficacy of 59% (95% CI 41% to 71%) than live vaccines but similar effectiveness: 36% (95% CI 24% to 46%). In children under two, the efficacy of inactivated vaccine was similar to placebo. Thirty-four reports containing safety outcomes were included, 22 including live vaccines, 8 inactivated vaccines and 4 both types. The most commonly presented short-term outcomes were temperature and local reactions. The variability in design of studies and presentation of data was such that meta-analysis of safety outcome data was not feasible. AUTHORS’ CONCLUSIONS: Influenza vaccines are efficacious in children older than two years but little evidence is available for children under two. There was a marked difference between vaccine efficacy and effectiveness. That no safety comparisons could be carried out emphasizes the need for standardisation of methods and presentation of vaccine safety data in future studies. It was surprising to find only one study of inactivated vaccine in children under two years, given recent recommendations to vaccinate healthy children from six months old in the USA and Canada. If immunisation in children is to be recommended as public-health policy, large-scale studies assessing important outcomes and directly comparing vaccine types are urgently required.

PMID: 16437500 [PubMed – indexed for MEDLINE]

1: Arch Pediatr Adolesc Med. 2008 Oct;162(10):943-51. Links

Influenza vaccine effectiveness among children 6 to 59 months of age during 2 influenza seasons: a case-cohort study.

Szilagyi PG, Fairbrother G, Griffin MR, Hornung RW, Donauer S, Morrow A, Altaye M, Zhu Y, Ambrose S, Edwards KM, Poehling KA, Lofthus G, Holloway M, Finelli L, Iwane M, Staat MA; New Vaccine Surveillance Network.

Strong Memorial Hospital, Rochester, NY 14642, USA. peter_szilagyi@urmc.rochester.edu

OBJECTIVE: To measure vaccine effectiveness (VE) in preventing influenza-related health care visits among children aged 6 to 59 months during 2 consecutive influenza seasons. DESIGN: Case-cohort study estimating effectiveness of inactivated influenza vaccine in preventing inpatient/outpatient visits (emergency department [ED] and outpatient clinic). We compared vaccination status of laboratory-confirmed influenza cases with a cluster sample of children from a random sample of practices in 3 counties (subcohort) during the 2003-2004 and 2004-2005 seasons. SETTING: Counties encompassing Rochester, New York, Nashville, Tennessee, and Cincinnati, Ohio. PARTICIPANTS: Children aged 6 to 59 months seen in inpatient/ED or outpatient clinic settings for acute respiratory illnesses and community-based subcohort comparison. Main Exposure Influenza vaccination. MAIN OUTCOME MEASURES: Influenza vaccination status of cases vs subcohort using time-dependent Cox proportional hazards models to estimate VE in preventing inpatient/ED and outpatient visits. RESULTS: During the 2003-2004 and 2004-2005 seasons, 165 and 80 inpatient/ED and 74 and 95 outpatient influenza cases were enrolled, while more than 4500 inpatient/ED and more than 600 outpatient subcohorts were evaluated, respectively. In bivariate analyses, cases had lower vaccination rates than subcohorts. However, significant influenza VE could not be demonstrated for any season, age, or setting after adjusting for county, sex, insurance, chronic conditions recommended for influenza vaccination, and timing of influenza vaccination (VE estimates ranged from 7%-52% across settings and seasons for fully vaccinated 6- to 59-month-olds). CONCLUSION: In 2 seasons with suboptimal antigenic match between vaccines and circulating strains, we could not demonstrate VE in preventing influenza-related inpatient/ED or outpatient visits in children younger than 5 years. Further study is needed during years with good vaccine match.

PMID: 18838647 [PubMed – indexed for MEDLINE]