TORONTO -- News that an unvaccinated Ontario boy is in hospital with a dangerous tetanus infection is prompting calls from worried parents seeking information on how to get their children vaccinated.

And in another Ontario community, catch-up vaccination clinics were being held Monday in a couple of schools where six children have been diagnosed with the mumps.

The tetanus case was a six-year-old boy from Owen Sound, Ont., about a 2 1/2-hour drive northwest of Toronto. The unidentified child had never been vaccinated against tetanus, a painful and life-threatening condition better known as lockjaw.

The boy had been transferred to London, Ont., for intensive care. But his condition has improved and he was moved to a pediatric care bed over the weekend, said Dr. Christine Kennedy, associate medical officer of health for the Grey Bruce Health Unit.

Kennedy said the unit has had numerous inquiries about vaccinations since word of the tetanus case hit the news over the weekend.

Tetanus is an infection caused by the bacterium Clostridium tetani. C tetani spores are ubiquitous, found in soil, dust and manure; infection occurs when spores make their way into a cut or a wound.

The name lockjaw comes from the severe muscle contractions that are triggered by the toxin the bacteria produce. The spasms are so strong, in fact, that people can suffer broken bones. They can also interfere with breathing.

Tetanus infections are fatal in a significant portion of cases, with the rate varying among different age groups. In young children, between 20 and 30 per cent of infections lead to death, said Dr. Shelley Deeks, Public Health Ontario's medical director for immunization and vaccine preventable disease.

"It is a very awful disease," Deeks said.

There is no specific remedy for tetanus, though people who contract the infection may be given an anti-toxin and are often treated with sedatives to control the spasms.

Once more common, tetanus is now rare because most people are vaccinated against it.

Children are supposed to get four doses of vaccine containing tetanus protection. The vaccine for children is generally combined with others that protect against diphtheria, pertussis (whooping cough), hemophilus influenzae type B and polio. Adults need tetanus booster shots every 10 years.

Everyone needs to be vaccinated against tetanus because the disease is not one where so-called herd immunity can develop, Kennedy noted.

When high levels of children are immunized against some diseases -- mumps or chickenpox, for instance -- you would not expect to see many cases; when few people are susceptible, diseases cannot easily spread.

But tetanus doesn't transmit from person to person. It is contracted when a vulnerable person is exposed to C. tetani bacteria. That means that even if 95 per cent of children were vaccinated, the remaining five per cent would still be at risk.

Meanwhile, health authorities in Guelph, Ont., are investigating an outbreak of mumps among students of three local schools. So far six children -- five teenagers and one elementary school student -- are confirmed to have been infected.

All six had received the recommended two doses of mumps-containing vaccine, said Dr. Nicola Mercer, medical officer of health for Wellington-Dufferin-Guelph Health Unit. Even with two doses of mumps vaccine, some people will contract the disease if exposed to the virus.

Health authorities in Guelph set up catch-up clinics in the affected schools on Monday, offering vaccinations to all children who were either unvaccinated or under-vaccinated -- meaning they had not had all doses of all recommended vaccines. Mercer said roughly 97.5 per cent of the children in the affected schools had received two doses of mumps vaccine.

Mercer said it is not currently known how the outbreak started, though it is assumed the virus was imported from outside of Canada. The mumps virus is not endemic -- meaning it does not constantly circulate -- in this country.

However, the first known case in this cluster had not recently travelled outside of Canada. Mercer said it is possible the person who imported the virus did not come to the attention of the medical community. Not everyone who contracts mumps has the tell-tale puffed-out cheeks.