To rule out confounding, observational studies of influenza vaccine need to include analyses during the "preinfluenza period".
Jackson
Michael L
ML
Weiss
Noel S
NS
Nelson
Jennifer C
JC
Jackson
Lisa A
LA
D000328:Adult; D000368:Aged; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000209:etiology / Q000517:prevention & control*
D007252:Influenza Vaccines