But when this period finishes, countries have to pay full and some expensive vaccines such as for pneumococcal disease – which can cost up to $50 per dose – may be out of their reach, the report warns.
By 2020 the number of countries eligible for support from Gavi will have fallen from 73 to 53.
MPs are warning that despite the transition period immunisation rates in some middle-income countries are still stalling.
Dr Philippa Whitford, chair of the all party group and Scottish National Party MP for Central Ayrshire, said just using a country’s gross national income (GNI) as the basis for whether it should have access to support was too crude a measure as many middle income countries had extreme inequality.
“Gavi should look at access to vaccines across the country – what percentage of children are getting vaccines, does the country have areas of conflict or extreme poverty?
“Gavi should be looking at countries in the round rather than just basing their support on whether the capital city has a lot of money,” she said.
The report also highlights the growing trend of “vaccine hesitancy” – refusal of or scepticism about vaccines – in countries whatever their economic status.
A recent study that only 14 countries in the world reported no vaccine hesitancy.