The MMR vaccine is more effective after 12 months, i.e. there are fewer cases of the vaccine failing to confer immunity when first administered at 12 mos as opp

The MMR vaccine is more effective after 12 months, i.e. there are fewer cases of the vaccine failing to confer immunity when first administered at 12 mos as opposed to earlier. You can receive a first MMR dose earlier than 12 mos for certain grounds (e.g. international travel, military postings) but it is then recommended that the infant receive a second 'first dose' after 12 months.