The Chiapas state government yesterday said the dead children were both just a year old. One of the sick is in critical condition and 14 others are in serious condition.
A Catholic group, People who Believe, said a one month-old boy and a girl of the same age had died after receiving vaccinations in La Pimienta, a Simojovel village of Tzotzil Maya indigenous people.
Mexico's southernmost state has a large population of indigenous Maya groups. Those who are in mountain villages often have no easy or routine access to medical care.