This paper explores how intra-household dynamics relate to attitudes toward vaccines in low-income countries, by drawing on three novel surveys from Zambia. The first is a nationally representative, in-person survey of over 10,000 households that asked all household members individually about their willingness to get a COVID-19 vaccine. The second and third surveys involved conducting randomized experiments with over 2,000 participants using Facebook and SMS messages. They 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 intra-household dynamics. These data sources showed that people's willingness (unwillingness) to get a COVID-19 vaccine was strongly associated with whether other household members were also willing (unwilling). Both experiments found that respondents who received information emphasizing either individual or household benefits from getting a COVID-19 vaccine were 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 who were involved in household decision making. There was also some 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 although household members tend to have similar attitudes toward vaccines, communicating accurate information about the benefits of getting vaccinated can counter intra-household dynamics that undermine acceptance.