Newly obtained documents indicate that the US health secretary, Robert F Kennedy Jr, lied during two congressional hearings last year, when he told lawmakers who held the key to his confirmation that a 2019 visit to Samoa had “nothing to do with vaccines”.

Letters obtained by the Guardian and the Associated Press contradict that testimony. In one he wrote to the Samoan prime minister before the trip, Kennedy explicitly said he wanted to study the measles, mumps and rubella (MMR) vaccine in the Pacific island nation. In it, he used the words “vaccine” or “vaccination” eight times.