Transition from Free to Paid Vaccination: Willingness to Pay for COVID-19 Booster Doses in Vietnam in the Post-Pandemic Era.

Objective: As COVID-19 transitions to an endemic stage, low- and middle-income countries face fiscal challenges in sustaining fully subsidized vaccination programs. This study aims to estimate the willingness to pay (WTP) for COVID-19 booster doses and identify determinants of demand among Vietnamese adults during the transition to a user-fee mechanism. Methods: A cross-sectional survey was conducted in 2024 in Thanh Hoa Province, Vietnam, involving 405 adult participants recruited through convenience sampling from a single hospital setting. Data were collected through direct interviews using a structured questionnaire. The Contingent Valuation Method utilizing a double-bounded dichotomous choice format was employed to elicit WTP. Multivariable logistic regression was applied to determine factors associated with willingness to pay, while linear regression analysis was applied to examine determinants of the payment amount. Results: Among 405 participants, the estimated mean WTP for a COVID-19 booster dose was VND 410,046 (approx. US$ 15.7), whereas the median WTP was significantly lower at VND 201,307 (approx. US$ 7.7), indicating a right-skewed distribution. Multivariable logistic regression showed that married participants and those in higher income groups were more likely to report willingness to pay, whereas poor self-rated health and prior adverse events following vaccination were associated with lower willingness to pay. Linear regression analysis indicated that female participants and older individuals reported lower payment amounts, while those with a prior history of COVID-19 infection reported higher payment amounts. Notably, the median WTP was substantially lower than the estimated market price of imported mRNA vaccines, indicating a potential affordability gap between stated valuation and prevailing market prices for COVID-19 booster vaccination. Conclusion: These findings emphasize the necessity of flexible financing approaches to maintain vaccine uptake and prevent widening disparities during the transition to paid vaccination. As the study was conducted using convenience sampling at a single hospital, the findings should be interpreted with consideration of limited generalizability.