Throughout human history, epidemics and pandemics have resulted in untold suffering, localized reductions in population size, and damaged economies. Often, economic harm has caused greater loss of well-being than the infection itself. There are different categories of infectious diseases. They include:
Pandemic – an epidemic that spreads between countries (e.g., Covid-19 was an epidemic when it was limited to China, with global spread it became a pandemic); Epidemic – sudden increase in cases above the expected incidence in a region where the disease is not permanently prevalent and is spreading from person to person; Endemic – infection that is maintained at baseline level in a geographic area; the infectious agent is always present in the population; Outbreak – greater-than-anticipated increase in the number of cases of an endemic illness; if not quickly controlled, an outbreak can become an epidemic; Cluster – increase above the number of expected cases in a place or time period; Sporadic disease – disease that occurs infrequently and irregularly.
The development and widespread acceptance of vaccines is crucial in controlling disease caused by pathogenic organisms, especially those that acquire the capability of efficient human-to-human transmission. Despite the overwhelming evidence of safety, vaccines have been associated with a small degree of untoward reactions, even when the vaccine is properly manufactured, handled, and administered.
Randomized, controlled clinical trials (RCTs) offer the most direct evidence of vaccine safety and efficacy, yet a vaccine that has been shown to be safe in RCTs may be associated with an adverse event that does not occur until millions of doses have been administered. For example, consider that the incidence of Guillain-Barre syndrome (GBS) after administration seasonal flu vaccine is so low (estimated at less than 1 case of GBS per million doses of flu vaccine administered) that the available data does not permit a firm conclusion as to whether the vaccine causes GBS. Also consider, however, that because GBS also occurs as a complication of influenza, the overall risk of GBS may be lower in those who are vaccinated than in those who are not.
Because vaccines are neither 100% safe nor 100% effective at preventing disease, some people will misunderstand the relative risks and benefits of vaccination. The data shows that almost all severe adverse events reported after vaccination reflect a temporal association that is due to coincidence. The true cause of a serious adverse event is almost always attributable to an unrelated factor that would have occurred in the absence of vaccination but may be difficult to identify. A perfect case in point was the observation that in some children, symptoms of autism were noted to begin at about the age the first measles vaccine was administered, or about 12 to 15 months. This observation was interpreted incorrectly to support an autism – measles vaccine link. This association was thoroughly debunked.
For the first time in 2020, the CDC and FDA together issued an emergency use authorization (EUA) for Covid-19. This occurred because Covid-19 was recognized as a pandemic for which no vaccine was available. The vaccine became available after initial trials. The EUA was permissible based on the Public Readiness and Emergency Preparedness Act of 2005. Looking ahead, vaccines will be the best way to protect us from future epidemics.
By Peter Galvin, MGBLOG COMMENTS POWERED BY DISQUS