Drinking water does not prevent postvaccination presyncope in youth
Drinking water prior to vaccination does not appear to be effective in preventing postvaccination presyncope, a potential syncope precursor, in adolescents and young adults, according to a study.
Individuals aged 11 to 21 years who were receiving ≥1 intramuscular vaccine in primary care clinics were randomly assigned to the intervention group (n=901)—in which participants were encouraged to drink 500 mL of water, with vaccination recommended 10 to 60 minutes later—or the usual-care group (control; n=906).
All participants completed a 12-item survey during the 20-minute period postvaccination as part of presyncope symptom assessment. Symptoms were classified with a primary cutoff sensitive for presyncope, and a secondary, more restrictive cutoff requiring greater symptoms. All p-values were based on 1-sided tests.
Results revealed that none of the participants had syncope. Presyncope occurred in 36.2 percent of participants by using the primary definition, and in 8 percent by using the restrictive definition. Presyncope did not significantly differ by intervention group in terms of the primary (p=0.24) and restrictive outcomes (p=0.17).
Among participants in the intervention group who drank all 500 mL of water and vaccinated within 10 to 60 minutes after (n=519), there was no reduction in presyncope seen for the primary (p=0.13) or restrictive outcome (p=0.17).
Multivariable regression analysis found presyncope to be associated with younger age, history of passing out or nearly passing out after a shot or blood draw, prevaccination anxiety, receiving >1 injected vaccine, and greater postvaccination pain.
Researchers pointed out that while drinking water before vaccination did not help prevent postvaccination presyncope in adolescents and young adults, “the study did identify factors associated with postvaccination presyncope that could be targeted in future research to develop feasible and effective postvaccination presyncope and syncope prevention strategies.”