This is the VOA Special English Health Report.

When parents go to work, their young children often spend the day in child care. That contact with other children can make it easier to get sick. But new research suggests that this might have a protective effect a few years later when children start school.

A research team looked at data from a large study. That study followed the health of a group of Canadian children for almost their first ten years of life.

Sylvana Cote at the University of Montreal led the research team. She says some of the children were more likely to get sick from the kinds of infections commonly passed around a day care center. But she says these children were also more likely to avoid infections when they entered elementary school a few years later.

SYLVANA COTE: "Children who started child care early -- that is, before two and a half years -- and who attended child care where there were a large group of children, they have lower rates of infections than children who either never went to day care or children who went to small-group day care."

Sylvana Cote says her study was not really designed to explain why children who started day care early with many other children had fewer infections later. But she says there is a non-medical reason why getting sick early might be better: it reduces the risk of having to stay home from school.

SYLVANA COTE: "We argue in the paper that, you know, missing school when you're starting to read or when you learn to write may be more problematic for the future academic trajectory than missing day care days."

The research appears in the Archives of Pediatric and Adolescent Medicine, a journal of the American Medical Association.

Some diseases can be prevented by vaccines. This month, the World Health Organization launched the first vaccine ever developed for Africa.

The vaccine is designed to provide ten years of low-cost protection against meningococcal A. This bacterial form of meningitis can cause brain damage and death. Major epidemics strike Africa every seven to 14 years. Children and young adults are the hardest hit.

Last year, an outbreak across sub-Saharan Africa killed more than 5,000 people. The WHO says as many as 450 million people across Africa are at risk from meningitis.

The new vaccine is called MenAfriVac. It can be given to children as young as one, which is earlier than vaccines currently used to fight meningitis epidemics in Africa.

Health workers launched the new vaccine in Burkina Faso in West Africa. There are 25 countries along Africa's so-called meningitis belt from Senegal to Ethiopia. The hope is that people in all 25 countries will be protected against the disease by 2015.

trajectory: a path, progression, or line of development resembling a physical trajectory 轨迹

meningitis: a serious disease in which the tissues enclosing the brain and spinal cord become infected and swollen, causing severe headache, fever and sometimes death 脑脊膜炎；脑膜炎

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（来源：VOA 编辑：崔旭燕）