article_snippet.sent: But the protection waned over time, boosters worked less well than the initial dose and the vaccine was not as effective in younger children, a report in The Lancet journal says.
article_snippet.sent: Over three years, an average 558 cases were averted for every 1,000 infants vaccinated, and 983 cases in those also given a booster dose.
article_snippet.sent: But he said he was ‘disappointed’ by the results of the clinical trials, adding:
article_snippet.sent: I hoped the vaccine would be more effective, but we were never going to end up with the success seen in measles vaccines, with 97 per cent efficacy.