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| ● Introduction ● 25 years of vaccination against chickenpox in the United States [ver] ● Effect of vaccination on the incidence and severity of chickenpox in the US. [ver] ● Effect of universal varicella vaccination on the incidence of shingles in the US. [ver] ● In short… [ver] ● Smallpox vaccination in Spain [ver] ● More information [ver] |
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| ● A monographic supplement to J Infect Dis highlights the US experience with 25 years of chickenpox vaccination program ● Universal vaccination with two doses has shown an effectiveness of 99%: it dramatically reduced the incidence of the disease, even in non-vaccinated patients and in all ages, without any negative effect on the epidemiology of herpes zoster reduced. |
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introduction
It has recently been 25 years since the US introduced the chickenpox vaccine to its schedule in 1996. Magazine on the occasion of this anniversary The Journal of Infectious Diseases have recently published a monographic supplement titled: Varicella vaccination program in the United States: 25 years of saving lives and preventing disease (J Infect Dis. 2022;226 (supl 4), Nov/2022), which presents the experience of the vaccination program in the US, including epidemiological surveillance of chickenpox and herpes zoster, vaccination coverage, safety, and effectiveness, and its Economic impact included. Program.
Some of the most relevant material from this monograph are described below.
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25 Years of Vaccination Against Chickenpox in the United States
Mona Marin, an epidemiologist at the US CDC who has devoted her research to vaccines and, in particular, varicella, writes about the history of varicella vaccination (Marin M, J Infect Dis 2022).
In 1974, Japanese physician Michiaki Takahashi developed a live attenuated smallpox vaccine. Results from studies conducted in Japan showed that the vaccine was safe, immunogenic and well-tolerated. However, it met marked and widespread resistance in Western countries, considering that this vaccine had significant potential risks as it could favor reactivation of the virus and cause an increase in herpes zoster (HZ). Furthermore, since the duration of protection obtained is unknown, it may be the case that vaccinated people lose their immunity over time and develop chickenpox in adulthood, when the disease is more likely to have complications. For this reason, in 1979 a group was formed in the United States to study this vaccine (Collaborative Varicella Vaccine Study Group), who concluded a few years later that the vaccine was safe, produced a potent antibody response (as measured by FAMA –fluorescent antibodies to membrane antigens-) and no cases of HZ were observed between vaccinations.
After that, various clinical trials started, both in America and Europe. With the results achieved, the US was the first country to incorporate the chickenpox vaccine into its program. Both the American Academy of Pediatrics (AAP) in 1995 and the Advisory Committee on Immunization (ACIP) in 1996 recommended vaccinating healthy children with a single dose at 12–18 months of age and preventive vaccinations before 13 years of age. The disease did not pass. It was found that the effectiveness of the vaccine was close to 97% with a 90% reduction in cases. However, outbreaks and cases of chickenpox began to be detected in previously vaccinated people (Varicella crack), which led to a change in vaccination policy to a 2-dose schedule (12–15 months and 3–4 years) in 2007 (Marin M, MMWR Recom Rep 2007). This second dose markedly improved the humoral and cellular immune response, which correlated with an increase in vaccine effectiveness, which is now estimated at 99%.
Twenty-five years after the introduction of the chickenpox vaccine in the United States, the incidence of the disease has decreased by more than 97% in all age groups. An added benefit is that the risk of developing HZ is reduced in those who get vaccinated. Since 1995, the US chickenpox vaccination program has prevented 91 million cases of chickenpox, more than 238,000 hospitalizations and approximately 2000 deaths.
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Effect of vaccination on the incidence and severity of chickenpox in the US.
Monitoring of the effect of varicella vaccination between 1995 and 2019 has shown the following (Marin M, J Infect Dis 2022):
- In 2005, after 5 years of implementation of the varicella vaccination program with a single dose, the incidence of the disease had decreased by 90%. This reduction reached 97% after the introduction of the 2-dose regimen.
- Epidemiological surveillance data suggest that the decline is more marked in children and adolescents, but that it extends to all age groups and those who have not been vaccinated.
- Particularly in those under the age of 20, hospitalizations and deaths decreased by 94% and 97%, respectively.
- The effects of vaccination also include a reduction in the spread of the virus and an increase in community safety.
- No loss of protection has been observed in vaccinated subjects.
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Effect of universal vaccination against varicella on the incidence of herpes zoster in the US.
One of the initial questions raised when the universal vaccination program against chickenpox was introduced was its impact on the epidemiology of HZ (Leung J, J Infect Dis 2022).
This article summarizes the incidence of HZ in people over 30 years old (born before 1990 before vaccination) and in people 1–29 years old (born after 1990 after vaccination) during 1998–2019. Analyzes and compares. The study results refute the initial hypothesis that vaccination may increase the incidence of HZ among adults who were already exposed to chickenpox (the pre-vaccination group), as no increase in HZ cases was observed in any age group And indeed, the incidence of HZ decreased in the vaccinated group (see attached figure).
The authors believe that universal vaccination will reduce HZ cases in the entire population in the coming years.
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summary …
In short, the passage of time has removed some of the concerns that this vaccine generated in its infancy. 2-dose vaccination produces dietary protection that is maintained over time; No displacement of the disease or increase in HZ cases in adulthood has been observed.
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Varicella Vaccination in Spain
In Spain, varicella vaccination has had to go through a zigzag path from the initial recommendation of vaccination for high-risk people (in 1998) to the current status, even going through a period in which it was approved for special use. The distribution of the vaccine was restricted. Hospitable.
Since 2016, the vaccination schedule includes 2 doses (15 months and 3-4 years). The average coverage for the first dose in 2021 was 93.5% (2017 cohort), although this decreased to 87.4% for the second dose (2015 cohort) (Ministry of Health, 2022).
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More information on this website
bibliographic reference
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