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What is the history of chickenpox in America and other countries?
Herpesvirologists believe that the chickenpox (varicella) virus originated in Africa millions of years ago. In 1767, English physician William Heberden definitively differentiated chickenpox from smallpox and reported lifelong immunity to the illness upon recovery from the infection. In 1875, Rudolf Steiner discovered that chickenpox was infectious to others after he took liquid from the chickenpox blisters of an infected individual and spread it to healthy volunteers. The first association between shingles and chickenpox was noted in 1888, after Von Bokay found that children with a negative history of chickenpox developed the infection after exposure to shingles. In 1954, Dr. Thomas Weller isolated the varicella virus in both chickenpox and shingles lesions.
In 1951, when the CDC reported on its plan to revise morbidity reporting by states, chickenpox was not considered significant enough of a disease to be listed as part of the “Minimum List for National Reporting.” Deaths related to chickenpox were still being reported and between 1950 and 1959, an average of 114 chickenpox-associated deaths were reported annually. When chickenpox became a nationally notifiable disease in 1972, 164,114 cases were reported to the CDC. Public health officials, however, estimated that nearly 4 million infections actually occurred each year, which resulted in approximately 100 deaths and 10,000 hospitalizations.
In the late 1970’s, the CDC became aware of a potential association between the use of aspirin during an illness such as chickenpox or influenza, and Reye syndrome, a rare illness that can affect the liver, blood, and brain, and lead to coma and brain death. By June of 1982, evidence supported these findings, which prompted the U.S. Surgeon General to issue a warning against the use of aspirin and aspirin-containing products by children during an influenza or chickenpox illness.
In 1981, chickenpox was removed from the weekly morbidity report, and individual states were encouraged to report the number of cases on an annual basis. This change in reporting requirements was noted by the CDC to coincide with a decrease in the number of states reporting chickenpox illness. In 1972, 46 states and the District of Columbia (D.C.) were reporting chickenpox cases on a weekly basis; however, by 1997, only 20 states and D.C. were submitting data, which significantly decreased the reliability of national chickenpox rates.
In the 25 years prior to the licensing of the chickenpox vaccine, there were a total of 2,262 deaths, an average of 90 deaths per year, associated with chickenpox infections. 59 percent of deaths occurred in adolescents and children under the age of 20, and death rates were highest among Caucasians. However, death rates, when compared to the number of infections, were found to be highest among adults, and were followed by children younger than 12 months of age. Death rates were also noted to be highest between March and May, and lowest between August and October.
From 1970 to 1994, the year prior to the licensing of the chickenpox vaccine, death from chickenpox decreased by between 51.3 and 72.2 percent among persons of all ages, but especially among adults who developed the illness. Death rates were found to be higher among foreign-born adults, especially those who had immigrated to the U.S. from tropical climates where chickenpox infections are frequently seen in adults rather than in children. 27.5 percent of chickenpox-associated death certificates reported a pre-existing medical condition, with cancer being the most frequently listed comorbidity.
Death from chickenpox-related pneumonia was most frequently reported (27.6 percent) and was followed by central nervous system (CNS) complications (21.1 percent). Of these CNS complications, nearly 9 percent were confirmed to be the result of Reye syndrome, acknowledged by the U.S. Surgeon General in 1982 to be associated with the use of aspirin-containing products in children with chickenpox. During this time period, the overall annual death rate from chickenpox was estimated at 0.4 deaths per 1 million population.
In 1996, at the time of the CDC’s Advisory Committee on Immunization Practices (ACIP) recommendation for routine administration of the newly licensed chickenpox vaccine, the CDC reported that an estimated 3.7 million cases of chickenpox occurred annually. However, as the illness was not nationally notifiable, the CDC also admitted that surveillance data was limited and estimated that only 4-5 percent of illnesses were actually reported. In response, the CDC established 3 active surveillance sites to monitor the impact of the vaccine, in Antelope Valley, California, Travis County, Texas and West Philadelphia, PA.
According to the CDC, by 2000, as chickenpox vaccination rates climbed to 74-84 percent of all 19 to 35-month olds in the active surveillance site communities, chickenpox infections decreased significantly. In 2003, the year when chickenpox infections returned to the nationally notifiable disease list, only 20,948 cases were reported. The CDC also reported that for the four states (Texas, Michigan, Illinois, and West Virginia) which had consistently submitted chickenpox infection data since 1990, each had reported the lowest number of cases on record. Increased use of the chickenpox vaccine, especially among preschool children, was credited for the decrease.
Active surveillance of chickenpox continued at two of the three original surveillance sites set up in 1995 to monitor the impact of the chickenpox vaccine. From data collected between 1996 and 2005, site investigators noted that as vaccination rates increased to approximately 90 percent among the two remaining surveillance sites, the number of chickenpox infections also increased among vaccinated individuals, from two percent to 56 percent. The age of the illness of those infected also shifted, with most infections occurring in children between 9 and 11 years, instead of in younger children, who were previously noted to have higher infection rates prior to the introduction of the chickenpox vaccine.
After recovery from chickenpox, the virus will remain dormant in the sensory nerve ganglia of the body. The virus, however, can re-activate as shingles (herpes zoster), a painful rash that typically presents on one side of the body or face, and can result in complications including vision loss, balance or hearing issues, and postherpetic neuralgia (PHN) – a condition which causes severe and often long-lasting pain at the site of the shingles rash.
Exposure to a circulating strain of chickenpox virus (e.g. contact with a sick child) boosts the immune response in a person with a prior history of chickenpox illness, and this can delay or even prevent shingles infection. When routine use of the chickenpox vaccine was recommended in 1996, the CDC reported that only 15 percent of adults would ever experience shingles at some point in their lifetime. The FDA, in their summary report to support the approval of the chickenpox vaccine, expressed concerns that the vaccine might lead to a significant rise in shingles cases and recommended that health officials monitor shingles rates following the vaccine’s introduction.
The CDC, however, chose not to monitor shingles infections at any of the three active surveillance sites in 1995. Five years later, in 2000, shingles surveillance was finally added to California’s Antelope Valley Varicella Active Surveillance Project (AV-VASP), at a time when chickenpox rates had declined by 70 percent. By 2000, the number of reported shingles infections had already increased dramatically in adults 20 to 69 years, and children with a prior history of chickenpox illness were found to have shingles rates similar to the adult population. Over a three-year period, from 2000 to 2002, the number of reported shingles cases increased by 56 percent, an 18 percent yearly increase. Additionally, a CDC-sponsored study completed in Massachusetts found that between 1998 and 2003, as chickenpox vaccine use increased and chickenpox infection rates decreased, the overall rate of shingles infections increased by 141 percent among all age groups. The incidence of shingles among adults between 25 and 44 years increased by 161 percent, while rates among children and young adults aged 1 to 24 years increased by 152 percent.
From 2001 to 2005, multiple outbreaks of chickenpox illness among fully-vaccinated school children were reported and vaccinated students were frequently found to be responsible for the outbreaks. The CDC reported the vaccine to be between 72 and 85 percent effective; however, in some schools, up to 40 percent of vaccinated students in one classroom developed chickenpox. While many cases were reportedly mild, up to 30 percent were not, and vaccinated students were found to have chickenpox symptoms similar to children who developed natural chickenpox illness. At least two chickenpox-related deaths were reported among vaccinated children who developed chickenpox as a result of vaccine failure.
The CDC reported that vaccinated children with breakthrough illness (resulting in less than or equal to 50 lesions) were two-thirds less likely to transmit the illness when compared to vaccinated children who developed more than 50 lesions; however, they also acknowledged that the illness could be mild enough to delay diagnosis and isolation. As a result, undiagnosed cases of mild chickenpox infections had the potential to result in a higher rate of transmission within a community.
In June 2006, in response to the significant rise in chickenpox illness among vaccinated children, ACIP voted to recommend a second dose of chickenpox vaccine be administered to all children prior to school entry, at age 4-6 years, and recommended that all persons previously vaccinated with one dose of chickenpox vaccine receive a second dose.
Following the booster dose recommendation, the CDC determined that the two remaining chickenpox active surveillance sites were not sufficient enough to monitor the impact of the two-dose chickenpox vaccine recommendation and opted instead to examine chickenpox data collected from the National Notifiable Diseases Surveillance System (NNDSS). However, as chickenpox was not a nationally notifiable disease until 2003, the NNDSS could not be considered a reliable data source for chickenpox surveillance data.
As a result, the CDC came up with ad hoc criteria to decide whether a particular state’s data could, in fact, be considered an accurate reflection of the true number of reported chickenpox cases. Only states reporting at least one case of chickenpox per 100,000 population for at least three consecutive years, between 2000 and 2010, were considered in the analysis of NNDSS data. This meant that only 31 of the 39 states reporting chickenpox infections to NNDSS could be included. From the 31 states, the CDC reported that chickenpox infections decreased by 43 percent between 2000 and 2005, following the single-dose vaccine recommendation, and by 72 percent between 2006 and 2010 following the booster dose recommendation. Overall, chickenpox rates were reported to have decreased by 79 percent between 2000 and 2010.
In 2010, 15,427 chickenpox infections were reported to the NNDSS. Vaccination status was known for 32 percent of all reported cases, and of these cases, 60 percent occurred in persons with a prior history of chickenpox vaccination. Of the cases which occurred among previously vaccinated individuals, only half were considered mild. Four chickenpox-related deaths were reported in 2010.
While cases and outbreaks of chickenpox have decreased, the number of shingles infections have significantly increased, with the CDC reporting that they do not know the reason for this increase. Several published studies, however, note that shingles cases have increase significantly since the introduction and uptake of the chickenpox vaccine. While shingles is not, and has never been a nationally notifiable disease, the CDC currently reports that 33 percent of people are at risk for developing shingles in their lifetime, up from the 15 percent previously reported in 1996, at the time of the ACIP recommendation for routine use of the chickenpox vaccine.
In 2019, 8,297 cases of chickenpox and 6 deaths were reported by 39 states, the District of Columbia, and 2 U.S. territories. One death and 2,952 chickenpox cases were reported in 2020.
Globally, the World Health Organization (WHO) reports that in temperate climates, most cases of chickenpox occur before the age of ten. The WHO also reports the illness to be mild and generally self-limiting, but states that severe complications can occur, more frequently among infants and persons with immunosuppression.
Many European countries do not recommend routine use of the chickenpox vaccine, and most individuals residing in these countries will develop the illness during childhood. In the United Kingdom (UK), where routine chickenpox vaccination is not recommended, health officials consider the illness to be mild and report that most infected children recover within a week, without the need to see a doctor. UK public health officials state their decision to not routinely recommend chickenpox vaccine was based on concerns that a decrease in chickenpox rates would put unvaccinated children at risk of developing the illness as adults, when complications can be more severe. They also report that widespread use of the chickenpox vaccine would significantly increase the rate of shingles among adults.
IMPORTANT NOTE: NVIC encourages you to become fully informed about Chickenpox and the Chickenpox vaccine by reading all sections in the Table of Contents , which contain many links and resources such as the manufacturer product information inserts, and to speak with one or more trusted health care professionals before making a vaccination decision for yourself or your child. This information is for educational purposes only and is not intended as medical advice.