A recent study made interesting observations on why pandemic flu vaccination programs may lose their effectiveness. They feel that the public incorrectly link pandemic vaccination campaigns with coincidental and unrelated health events with the vaccines, thus undermining the effectiveness of the programmes.
Authored by an international team of investigators led by Cincinnati Children's Hospital Medical Center, the study reviewed medical data from prior studies and from hospital databases to identify background rates of health events that occurred without any vaccine.
"Regardless of whether someone gets the vaccine, bad things happen to people every day and generally occur at fairly predictable rates. 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," said Dr. Steven Black, lead author and a physician in the Center for Global Health and Division of Infectious Diseases at Cincinnati Children's.
The review showed the rates of adverse events varied by year, country, age and sex of the population.
And for the authors the problem is that public concern regarding medical events can interfere with important vaccine programs, even if the vaccine is not the cause.
They cited one example of the interruption of a 2006 seasonal influenza campaign in Israel, where four deaths occurred within 24 hours of immunization.
The clustering of fatalities and close timing of vaccination resulted in global news coverage, public trepidation and compromised the inoculation campaign.
But in reality, the four patients who died all were in a group already at high risk for sudden death from age and underlying medical conditions.
Their deaths were consistent with a cardiac cause of death, and the number of deaths was lower than would be expected normally for such a high-risk population.
The authors also revisited one of the concerns raised during the 1976-77 swine flu vaccination program.
The vaccine in that campaign was associated with an increased number of Guillian-Barre Syndrome cases, in which the body's immune system mistakenly attacks part of the nervous system.
"The reporting of even a fraction of such a large number of case as adverse events following immunization, with attendant media coverage, would likely give rise to high levels public concern, even though the occurrence of such cases was completely predictable and would have happened in the absence of a mass campaign," said the paper.
To help address these concerns, health agencies are creating systems to gather and accurately assess data on background health events when evaluating vaccine safety.
"In the heat of the moment of a pandemic vaccination campaign, the public isn't good at evaluating comparative risk or realizing that obviously some people die or develop serious illnesses every day. By putting background rate data into proper context, we want to help people make an informed decision about pandemic flu vaccinations," said Black.
The study has been published in the Lancet.