Thimerosal in Vaccines
Since the 1930s, thimerosal has been added to some vaccines and other products as a preservative because it is effective in killing bacteria and in preventing bacterial contamination, particularly in multidose containers. When thimerosal is degraded or metabolized, one product is ethyl mercury, an organic derivative of mercury. The only known side effects of receiving low doses of thimerosal in vaccines have been minor reactions such as redness and swelling at the injection site.
In July 1999, U.S. Department of Health and Human Service agencies, The American Academy of Pediatrics, and vaccine manufacturers agreed that thimerosal should be reduced or eliminated in vaccines as a precautionary measure and to reduce exposure to mercury from all sources. The decision to move toward reduced or eliminated thimerosal in vaccines was based on the various Federal guidelines for methyl mercury exposure and the assumption that the health risks from methyl and ethyl mercury were the same.

Ethyl vs. Methyl Mercury

Early in the 2009 H1N1 influenza pandemic, an editorial in Eurosurveillance noted the importance of observing experience with this novel virus in the southern hemisphere during their usual winter influenza season [1].

This special issue of Eurosurveillance is a timely response to that call. It contains reports from the island of Réunion, South Africa, South America (Brazil, Peru), and Australia (New South Wales and Victoria). It also includes an overview of the effect of the pandemic on indigenous people. This editorial summarises some of the key findings from these papers, reviews features of pandemic H1N1 influenza epidemiology in these countries, and lists some potential lessons for the northern hemisphere (and possible future waves in the southern hemisphere).

 Important findings from the papers in this issue

The effectiveness of pandemic flu vaccination campaigns -- like that now underway for H1N1 -- could be undermined by the public incorrectly associating coincidental and unrelated health events with the vaccines.

This is the conclusion of a paper published online Oct. 31 by the Lancet and authored by an international team of investigators led by Cincinnati Children's Hospital Medical Center.

"Regardless of whether someone gets the vaccine, bad things happen to people every day and generally occur at fairly predictable rates," said Steven Black, M.D., lead author and a physician in the Center for Global Health and Division of Infectious Diseases at Cincinnati Children's. "Identifying real safety concerns with new vaccines means we have to untangle actual safety signals from background medical events, which are those that would happen without vaccination."

A “perplexing” Canadian study linking H1N1 to seasonal flu shots is throwing national influenza plans into disarray and testing public faith in the government agencies responsible for protecting the nation's health.

Distributed for peer review last week, the study confounded infectious-disease experts in suggesting that people vaccinated against seasonal flu are twice as likely to catch swine flu.

The paper is under peer review, and lead researchers Danuta Skowronski of the British Columbia Centre for Disease Control and Gaston De Serres of Laval University must stay mum until it's published.

Met with intense early skepticism both in Canada and abroad, the paper has since convinced several provincial health agencies to announce hasty suspensions of seasonal flu vaccinations, long-held fixtures of public-health planning.