3G Internet and Information Frictions in Childhood Vaccination: Evidence from India

Vaccination rates remain high for doses delivered during routine early-life contacts, yet fall sharply for vaccines scheduled months later in low-and middle-income countries. We study whether mobile internet helps parents keep track of the immunization schedule in settings where completing later doses requires active follow-up. Using data on about 101,000 children from India's National Family Health Survey (2019-21) and an instrumental-variable strategy based on terrain ruggedness, we estimate the effect of local 3G coverage on childhood vaccination. We find that positive effects are concentrated in vaccines scheduled at 16 months, when parents must remember the timing of a return visit, while earlier doses delivered during routine contacts show little systematic response. In particular, estimated effects are positive for second-dose measles vaccination (MCV-2), Japanese encephalitis vaccination (JE-2), and the DPT booster, and become larger when the sample is restricted to age-eligible children. A timing test shows that, for JE-2, the estimated effect of 3G is negative before 16 months and positive thereafter, consistent with improved schedule adherence. Effects are also larger among less educated mothers, suggesting that digital connectivity matters more where households have fewer baseline information resources. Overall, the results indicate that gaps in later childhood vaccination partly reflect information frictions and that mobile internet can help reduce them in low-and middle-income settings.