Measles in PEI

Measles is making a comeback in the Western world. As of March 25, 2014 the list includes 228 cases in Chilliwack BC, 10 in Saskatchewan, as well as outbreaks in Ottawa, Toronto, Manitoba, and PEI.

The news out of my home province is particularly disturbing for the near future, as the level of vaccination in newborns has dropped almost 12% percentage points below the national average (poor math by reporter in the article)

The measles vaccination rate for P.E.I. infants is 11 per cent below the national average, according to statistics from provincial and national health agencies.

P.E.I. health officials say 84 per cent of Island infants received the shot by the time they’re two years of age versus the 95 per cent national average.

The threshold for immunization levels that can effect herd or community immunity vary by disease and location, but the table below indicates that the vaccination rate should be well over 90%.

Vaccine-Preventable Disease Level of Community Immunity
Diphtheria 85%
Measles 94% or more
Whooping Cough 94%
Rubella  85%
Smallpox 85%

These numbers are not exact as there are several factors that affect the calculations:

  • The biologic properties of the viruses or bacteria: Some diseases are more easily transmitted than others, thus affecting community immunity thresholds. The greater the transmissibility, the higher the threshold needs to be to prevent spread of the disease.
  • The rate of contact among susceptibles and immunes in a population: Susceptibles are protected by community immunity only when they interact with immunes rather than with other susceptibles.
  • The number of susceptibles in the population: Immunes have to so far exceed the number of susceptibles in any community that contacts between susceptibles are rare events.

In the locations where the outbreaks have occurred, the Fraser Valley cases have been traced to a religious community that refused to vaccinate because their religion told them that the lives and health of their children was not important. In Ottawa, it has been linked to a traveller returning from the Philippines where there is currently a large widespread outbreak.

Measles is not a trivial disease as so many anti-vaxxers claim.

The Clinical Significance of Measles: A Review Walter A. Orenstein, Robert T. Perry and Neal A. Halsey J Infect Dis. (2004) 189 (Supplement 1): S4-S16.

 Abstract. Forty years after effective vaccines were licensed, measles continues to cause death and severe disease in children worldwide. Complications from measles can occur in almost every organ system. Pneumonia, croup, and encephalitis are common causes of death; encephalitis is the most common cause of long-term sequelae. Measles remains a common cause of blindness in developing countries. Complication rates are higher in those <5 and >20 years old, although croup and otitis media are more common in those <2 years old and encephalitis in older children and adults. Complication rates are increased by immune deficiency disorders, malnutrition, vitamin A deficiency, intense exposures to measles, and lack of previous measles vaccination. Case-fatality rates have decreased with improvements in socioeconomic status in many countries but remain high in developing countries.

PEI is dead last in some areas including wait times for common surgeries. If vaccination rates continue to decline, we may leap to the front in preventable diseases.

 

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One Response to Measles in PEI

  1. And it is happening in the US. See this http://www.cbsnews.com/news/measles-outbreak-in-orange-county-california-worst-in-decades/
    Its origin appears to be in Orange County, which is something like California’s Bible Belt.
    Here in BC, the epidemic started in the Fraser Valley (our Bible Belt). In particular , a member of one church has stated that vaccinating your children is defying the word of God, a being who apparently decides whether your child is a promising candidate to be the source of an infection that could potentially kill infants too young to receive the vaccine. Good ol’ God again.

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