Английская википедия считает, что в Японии прививается примерно каждый 5-й ребёнок, именно за счёт этого привитые получают "подкрепление" иммунитета. В Америке рекоменуют возобновлять прививку через 5 лет.
Some vaccinated children have been found to lose their protective antibody in as little as five to eight years.[29] However, according to the World Health Organization: "After observation of study populations for periods of up to 20 years in Japan and 10 years in the United States, more than 90% of immunocompetent persons who were vaccinated as children were still protected from varicella." However, since only one out of five Japanese children were vaccinated, the annual exposure of these vaccinees to children with natural chickenpox boosted the vaccinees' immune system. In the United States, where universal varicella vaccination has been practiced, the majority of children no longer receive exogenous (outside) boosting, thus, their cell-mediated immunity to VZV (varicella zoster virus) wanes—necessitating booster chickenpox vaccinations.[2] Some persons exposed to the virus after vaccine can experience milder cases of chicken pox (and usually then harbor both the attenuated vaccine or oka strain as well as the wild type or natural chickenpox strain which are both subject to reactivation as shingles).[30]
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timeasmymeasure
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Date: 2014-01-05 06:36 am (UTC)Some vaccinated children have been found to lose their protective antibody in as little as five to eight years.[29] However, according to the World Health Organization: "After observation of study populations for periods of up to 20 years in Japan and 10 years in the United States, more than 90% of immunocompetent persons who were vaccinated as children were still protected from varicella." However, since only one out of five Japanese children were vaccinated, the annual exposure of these vaccinees to children with natural chickenpox boosted the vaccinees' immune system. In the United States, where universal varicella vaccination has been practiced, the majority of children no longer receive exogenous (outside) boosting, thus, their cell-mediated immunity to VZV (varicella zoster virus) wanes—necessitating booster chickenpox vaccinations.[2] Some persons exposed to the virus after vaccine can experience milder cases of chicken pox (and usually then harbor both the attenuated vaccine or oka strain as well as the wild type or natural chickenpox strain which are both subject to reactivation as shingles).[30]
https://en.wikipedia.org/wiki/Varicella_vaccine