Health officials across the country are being told to stop using a common measles, mumps and rubella vaccine because it is being investigated for possible links to six cases of serious allergic reactions in patients in Alberta.
All six patients had received their vaccination from the same batch of MMR-II, a product sold by Merck Frosst Canada Ltd. They experienced anaphylaxis, a potentially life-threatening reaction characterized by swelling and difficulty breathing.
All were treated and have fully recovered. All five cases involved adults aged 20 to 30 in Alberta who had a previous history of allergy.
A joint investigation by Health Canada, the Public Health Agency of Canada and Health Alberta is being carried out with Merck Frosst, to see if the vaccine is having the same adverse reaction elsewhere in Canada.
It is asking doctors in Canada and other countries that use the product to report any adverse effects from use of MMR-II.
Investigation could take weeks
Dr. Arlene King, a director with the Public Health Agency said it would probably be several weeks before we have a complete analysis of both the adverse events and the product.
Health Canada has requested that the use of the lot involved be temporarily suspended, along with two other lots that were made with the same materials and that may be in use elsewhere in the country.
In total, about 200,000 doses of MMR-II are affected. Other lots of the vaccine remain available for use throughout the country.
Health Canada has also requested that Merck Frosst Canada provide a written report on any manufacturing or safety problems associated with the lot or its bulk components.
Albert is currently trying to contain an outbreak of the mumps, which has affected more than 150 residents so far. The province has been offering free mumps immunizations in two phases: first to post-secondary students, then to everyone in the high-risk population between the ages of 17 and 26.
People in this age group received only one dose of the mumps vaccine when they were children, which is now thought to have worn off. Those born before 1970 are assumed to have been exposed to the mumps virus at some point in their life and are therefore immune. Those younger than 17 have been vaccinated twice.
Karen Grimsrud, Alberta's acting chief medical officer of health, says the province has now halted the immunization campaign. Routine MMR immunizations will continue for one-year-olds as long as supplies of the vaccine are available.
"Based on Health Canada's analysis, we are suspending the use of these vaccine lots, and therefore have halted our campaign for 17 - 26-year olds, as well as students and staff of post-secondary institutions across the province," she said in a statement.
"Any adults already immunized against mumps are in no danger of reaction as anaphylaxis occurs very quickly after immunization."
Health Canada notes that serious reactions following MMR vaccinations are rare. Despite millions of doses administered in Canada since 1988, there have been only 21 reports of anaphylaxis following immunization.
