This paper explores how intra-household dynamics relate to attitudes towards vaccines in low and lower-middle income countries by drawing on two novel data sources from Zambia. The first is a nationally representative, in-person survey of over 10,000 households where all household members were individua This paper explores how intra-household dynamics relate to attitudes towards vaccines in low and lower-middle income countries by drawing on two novel data sources from Zambia. The first is a nationally representative, in-person survey of over 10,000 households where all household members were individually asked about their willingness to get a COVID-19 vaccine. The second is a randomized survey experiment with almost 3,000social media users that tested how the impact of information about the benefits from receiving a COVID-19 vaccine on people's willingness to get vaccinated varied based on intrahousehold dynamics. Both data sources showed that people's willingness (unwillingness) to get a COVID-19 vaccine was very strongly associated with whether other household members were also willing (unwilling). The experiment found that respondents who receivedinformation emphasizing either individual or household benefits from getting a COVID-19 vaccine were around 20 percent more willing to get vaccinated than those in the control group. This information was more potent among respondents who believed other members of their household would not get vaccinated but did not have a larger impact on respondents that were involved in household decision making. There was also evidence of positive “second-round” effects whereby respondents who received the information treatments were more likely to encourage other household members to get a COVID-19 vaccine. An important implication that flows from this analysis is that even though household members tend to have similar attitudes towards vaccines, communicating accurate information about the benefits of getting vaccinated can counter intra-household dynamics that undermine acceptance.