2-dose varicella vaccine regimen – decline of chickenpox

The varicella vaccine for chickenpox was introduced in the mid-1990’s in the USA and has been associated with substantial and statistically significant declines in incidence, hospitalizations and deaths attributable to chickenpox.

Despite the beliefs of vaccine refusers, who  have stated emphatically that chickenpox is not dangerous, the real complications from a varicella infection are numerous and serious:

  • dehydration
  • pneumonia
  • bleeding problems
  • infection or inflammation of the brain (encephalitis, cerebellar ataxia)
  • bacterial infections of the skin and soft tissues in children including Group A streptococcal infections
  • blood stream infections (sepsis)
  • toxic shock syndrome
  • bone infections
  • joint infections

Let’s take a look at the facts – the varicella vaccine has actually lead to a significant reduction in the incidence of chickenpox in children.

Varicella vaccine and decline of chickenpox

 

Despite the scientifically supported massive and dramatic decrease in chickenpox (and its related complications), in 2006, the Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC) recommended a change in the vaccine schedule to a 2-dose vaccine regimen to ensure that the immunity level was the highest. However, there was not much evidence whether the additional dose was necessary or would have any practical effect on the disease.

Therefore, researchers examined the incidence of varicella, as well as hospitalizations and outbreaks associated with it, in two areas of the USA, areas of California and Pennsylvania, and they found that varicella has declined significantly since the 2-dose vaccine recommendations was implemented. Stephanie R. Bialek, MD, MPH, from the National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia and coauthors wrote that, “declines in incidence across all ages, including infants who are not eligible for varicella vaccination, and adults, in whom vaccination levels are low, provide evidence of the benefit of high levels of immunity in the population.”

The researchers reviewed 1995-2010 epidemiological data from two active surveillance areas: Antelope Valley, California (outside of Los Angeles), and West Philadelphia, Pennsylvania. By 2010, varicella incidence in Antelope Valley was 0.3 cases per 1000 individuals compared with 1.1 in 2006, a statistically significant 76% decline in cases. Similarly, in West Philadelphia, the incidence had declined from 0.4 cases per 1000 in 2006 to 0.1 cases in 2010, also a statistically significant 67% decline. The data also showed a 98% decrease in chickenpox cases since 1995.

Additionally, the investigators reported that the incidence of varicella declined among all age groups, including infants not eligible to receive the vaccine, after introduction of the second dose which may be a possible indicator of the herd immunity from the vaccine.

Other important information from the article was that the varicella vaccination also appeared to curb the severity of the disease. Approximately 63% of individuals who received a single dose of the vaccine, but eventually contracted the disease (since the vaccine is not 100% effective), had 50 lesions or fewer, considered a very mild case. Approximately 70% of those patients who received 2 doses of the vaccine had fewer than 50 lesions. Over 50% of unvaccinated individuals had between 50 and 500 lesions.

The 2-dose regimen also appeared to reduce the risk for hospitalization: chickenpox-related hospitalizations declined more than 40% during 2006-2010 time period compared with 2002-2005, and by more than 85% compared with 1995-1998. Moreover, in the Antelope Valley, there are only 12 varicella outbreaks during the 2007-10 time period compared with 47 and 236 during the 2003-06 and 1995-8 time periods, respectively (a statistically significant difference).

Summary

The authors concluded that “full implementation of varicella vaccination recommendations across all age groups, including adolescents, adults, and women postpartum, remains critically important for ensuring the greatest possible protection of susceptible individuals at risk for severe varicella disease.”

For those antivaccine activists who think that chickenpox disappeared because of sanitation, or better medical care, or because of historical lies–I’ve just presented real, scientific evidence published in one of the highest quality journals out there. It’s a peer reviewed article that clearly shows, in less than 15 years time, the utter victory over a dangerous communicable diseases through vaccination. It’s clear. It’s science. And the science clearly shows the varicella vaccine saves lives.

 

Key citations

 

 

The Original Skeptical Raptor
Chief Executive Officer at SkepticalRaptor
Lifetime lover of science, especially biomedical research. Spent years in academics, business development, research, and traveling the world shilling for Big Pharma. I love sports, mostly college basketball and football, hockey, and baseball. I enjoy great food and intelligent conversation. And a delicious morning coffee!