On the bias of estimates of influenza vaccine effectiveness from test-negative studies.
Vaccine
; 35(52): 7297-7301, 2017 12 19.
Article
em En
| MEDLINE
| ID: mdl-29146382
ABSTRACT
Estimates of the effectiveness of influenza vaccines are commonly obtained from a test-negative design (TND) study, where cases and controls are patients seeking care for an acute respiratory illness who test positive and negative, respectively, for influenza infection. Vaccine effectiveness (VE) estimates from TND studies are usually interpreted as vaccine effectiveness against medically-attended influenza (MAI). However, it is also important to estimate VE against any influenza illness (symptomatic influenza (SI)) as individuals with SI are still a public health burden even if they do not seek medical care. We present a numerical method to evaluate the bias of TND-based estimates of influenza VE with respect to MAI and SI. We consider two sources of bias (a) confounding bias due to a (possibly unobserved) covariate that is associated with both vaccination and the probability of the outcome of interest and (b) bias resulting from the effect of vaccination on the probability of seeking care. Our results indicate that (a) VE estimates may suffer from substantial confounding bias when a confounder has a different effect on the probabilities of influenza and non-influenza ARI, and (b) when vaccination reduces the probability of seeking care against influenza ARI, then estimates of VE against MAI may be unbiased while estimates of VE against SI may be have a substantial positive bias.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Projetos de Pesquisa
/
Vacinas contra Influenza
/
Viés
/
Influenza Humana
/
Potência de Vacina
Tipo de estudo:
Observational_studies
/
Risk_factors_studies
Limite:
Humans
Idioma:
En
Revista:
Vaccine
Ano de publicação:
2017
Tipo de documento:
Article
País de afiliação:
Estados Unidos