Get the shot to stop whooping cough outbreaks
After the flu. whooping cough is the second most common infectious disease in Canada. While the disease often mimics a cold, it can be deadly to infants and young kids. Several provinces and at least one territory are battling outbreaks that some experts say are caused by low vaccination rates.
Quebec recorded more than 500 cases -- with the greatest number in the Laurentians and the Mauricie-Central Quebec region. That's several times the annual average. New Brunswick has had an outbreak in the Moncton area. PEI has had cases. Southern Manitoba has seen at least 44 cases out of more than 50 recorded by the province - up from 10 or so cases in a typical year. There have been cases in Yorkton, Saskatchewan. Alberta's North Zone has seen 239 cases so far this year - up from just 42 the year before. More modest increase have been reported in Calgary and Edmonton. BC has seen a small jump in cases as well; so has the Northwest Territories.
To some extent, we're going through an up cycle of whooping cough. For instance, BC is dealing with double the number of cases reported in 2012 but half the number reported in 2000. Alberta health officials have said part of the blame for outbreaks goes to the effectiveness of the vaccine. In 1997, Canada switched to a vaccine with fewer side effects, but one that becomes less effective over time. Roughly seven out of every 10 kids are fully protected for five years after getting their last dose. Central Alberta's chief medical officer says the protective effect may wear off just before kids get their Grade 9 booster provided by the province. Right out of the gate, pertussis vaccine is effective for up to eight or nine out of 10 children who receive it, which means that the vaccine fails in about 10 per cent of cases.
It's one factor in these outbreaks; what we're not sure of is how decisive a factor it is. Experts say that a major outbreak in California in 2010 (one that saw 10 infant deaths) may in part have been due to a sizeable number of unimmunized children. Also in 2010 in Saskatchewan, the incidence of pertussis in children under one year of age rose dramatically; under-immunization, particularly amongst some First Nations communities may have contributed to the jump. At least one expert has cited vaccine refusal in the Vancouver as a possible factor in an outbreak there. In Ontario, a localized outbreak in the southwestern part of the province was clearly linked to a community that refuses childhood immunization.
Whooping cough can be serious. Eighty per cent of the most dangerous complications from whooping cough occur in infants three months of age and younger. They include pneumonia, seizures and brain damage. The disease can lead to hospitalization and even death. Young infants are just getting started with immunizations, so they're at high risk of getting whooping cough by being exposed to an older child or adult who is infected. What we've seen is that many of the outbreaks thus far in Canada this year have affected those young kids we're most worried about. That's been the case in Manitoba. In the Mauricie-Central Quebec region, reports say close to a dozen elementary schools, two high schools and at least ten daycares in the region have had cases.
The fact we're seeing so many outbreaks says that whooping cough is in an up cycle. The most important thing is that everyone needs to be vaccinated. The more people who don't get vaccinated, the more likely it is that we'll see outbreaks. Kids need to be vaccinated at two, four, and six months of age, with boosters at 18 months, four to six years and 14 to 16 years of age. Since the vaccine's effect decreases over time, adults should talk to their doctor about having at least one added booster (along with tetanus and diphtheria) during their lifetime. The most important thing is to make sure infants get vaccinated on schedule. In the future, a vaccine that could be given to kids younger than two months might reduce dramatically the number of infants with whooping cough. But not yet.
Dr. Brian Goldman is host of White Coat, Black Art. Catch new episodes Saturdays at 1 pm (130 pm in parts of N&L); Sundays at 630 pm (730 pm AT and 8 pm in N&L) on CBC Radio One.