Chicken pox vaccination

The disease varicella is caused by a virus from the herpes virus group. The infection is extremely contagious. Reduction of the network of nurseries and kindergartens has led to the growth of the non-immune stratum (in England and the United States - 4-20% of people aged 20-25), so that chicken pox (chicken pox) in children, adolescents and adults has become common and proceeds with them heavier. Vaccination from chickenpox has significantly reduced the incidence of chicken pox.

After the primary infection, the varicella-zoster virus remains in the nerve ganglia and reactivates in the form of shingles when immunity decreases (immunosuppression, elderly age). In generalized form, the infection occurs in immunodeficiencies and immunosuppression. About the frequency of complications, data from the United Kingdom and Ireland show that 112 cases (frequency 0.82 per 100 000 children's population) were detected during the year: 40 children had septic or toxic shock, 30 pneumonia, 26 ataxia, 25 encephalitis, necrotizing fasciitis, 8 - DVS-syndrome, 9 - fulminant chickenpox. Five children died, 40% were discharged with residual manifestations (more often with ataxia and skin scars). Chickenpox provokes more than half of cases of necrotizing streptococcal fasciitis in children.

In Russia, 0.5-0.8 million children and adolescents carry the chickenpox annually (the incidence is 300-800 per 100,000), the damage in the form of quarantines and days of incapacity for work of parents is significant. Infection takes many lives of children on immunosuppression. The calculation of economic losses due to chickenpox showed that they are the second largest of all infectious diseases.

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The objectives of vaccination against varicella

Mass vaccination against chicken pox is included in the vaccination calendar of several countries (Japan, USA, Canada, Germany, etc.), where its economic effectiveness was proved. WHO recommends, first of all, to introduce selective vaccination of at-risk groups - leukemia patients in the period of remission and who are not ill or who are waiting for transplantation. This recommendation in Russia can be carried out, since the vaccine Varilrix was registered.

The feasibility of introducing vaccination against chickenpox was considered by a group of experts from Eastern European countries. Experts noted that chicken pox is an acute problem, including in the economic aspect. The emergence of a live attenuated vaccine based on the Oka strain in the arsenal of health systems opens up new possibilities for the prevention of chicken pox.

The accumulated experience of using preventive varicella vaccines in the world makes it possible to apply 3 prevention strategies:

• Selective vaccination of patients from at-risk groups of complicated chickenpox, representatives of occupational groups, family environment of immunocompromised patients and pregnant women. This strategy will protect the most vulnerable groups of patients, without affecting the overall morbidity and the formation of collective immunity, it will not reduce the economic burden of infection.
• Vaccination of contact persons in the outbreak will allow to control flares, first of all, in the DDU and schools. This strategy will also not affect the development of the epidemic process and the economic burden of the infection.
• Universal 2-dose vaccination of all children from 12 months of life in a strategic perspective will be able to provide economic benefits not only to a specific patient, but also to the population as a whole.

Immunity and effectiveness of vaccination against varicella

Introduction of a single dose Varilrix gives seroconversion in 95%, in people over 12 years - only in 78-82% of cases, two doses - in 99%, which justifies the introduction of 2 doses. In vaccinated children, once in contact, there are still cases of a "breakthrough" disease, which usually occurs easily. When it was administered simultaneously with Priori, a high seroconversion rate (95.7%) was observed with the same frequency of fever and exanthema. Okavax gives seroconversion in 98% after 1 dose, in 90% the duration of immunity is 20 years or more, the epidemic. The effectiveness in the 1st year is 100%, for the next 7 years after contact, 0.2-1.9% per year are ill, which is 5-15 times lower than in those not vaccinated. Varivax prevents the disease in 83-86% of the medium-heavy and severe - in 100. There is the question of a 2-fold vaccination, as is the case with other live viral vaccines; in countries that included vaccination in the calendar, it is carried out 2-fold. Mass vaccination in the United States reduced the incidence from 1995 to 2000. On 80%, most of all in the group of children 0-4 years. Simultaneous decrease in morbidity in the older age indicates the creation of collective immunity. The frequency of hospitalization decreased, and the death rate (by 1 million people) fell by 66% - from 0.41 in 1990-1994. To 0.14 in 1999-2001, and in children 1-4 years it was reduced by 92%.

There are fears that a decrease in the incidence of chickenpox may lead to an increase in the occurrence of shingles due to a decrease in the natural boosting of immunity in the survivors of chicken pox. These fears, however, were not confirmed. The possibility of vaccine prophylaxis of herpes zoster in elderly people is proved. In the US, since 2007, the vaccine Zostavax (Merck & Co.) has been included in the vaccination calendar for people over 60 years of age; the vaccine tests showed a reduction in the frequency of herpes zoster by 51% (from 11.1 to 5.4 per 1000) and postherpetic neuralgia by 67% (from 1.4 to 0.5 per 1000).

Vaccination of children with leukemia allowed to protect them during immunosuppressive therapy. Vaccination is performed with a remission of 1 year on the background of maintenance therapy (with a number of lymphocytes> 700 and platelets> 100 000). The level of seroconversion in them is above 92%, the epidemiological efficiency is 86%, 14% of the cases usually suffer from varicella without complications .. In vaccinated patients with varicella, the vaccine reduces the frequency of herpes zoster.

Vaccination from chicken pox: a characteristic of vaccines

Vaccines of chickenpox, registered in Russia

Vaccine	Composition
Varilrix is a living vaccine - Glaxo SmithKlein, England	Prepared from the strain of the Oka virus, modified by 38 passages on cell cultures; contains traces of neomycin, without gelatin. A 0.5 ml dose is administered subcutaneously or intramuscularly, starting at the age of 1 g., Is usually administered with other live viral vaccines. Store at 2-8 ° for 2 years.
Varivax® is a live vaccine from the Oka / Merck strain (Merck, Sharp & Dome, the Netherlands - is preparing to register)
Okavax is a live vaccine from the Oka strain - (Biken Institute, Japan, exclusive distributor in Europe - sanofi pasteur - is preparing for registration). There is no gelatin in the composition.

Reactions and contraindications for chickenpox vaccination

Reactogenicity of vaccines is low, within 1 month. After the introduction of Varilrix in 2-3% observed maculopapular, in 1% - vesicle rashes. When using Okavax vaccine in healthy patients, a rise in body temperature was observed in 2.8%, a rash in 1.7%, local reactions in 3.2% of cases. In persons with various pathologies, the reactions were noted in 3.5%, 3.5% and 0.9% of cases, respectively.

In patients with leukemia, rash elements, often single, occur in 24%. The vaccine virus can be detected in vesicles only in 1%. 4-5% of vaccinated patients have a temperature> 38.5 °, pain and redness at the injection site - in 20-30% of children. Shingles after vaccination are rarely detected.

Contraindications are the same as for other live vaccines, as well as immunosuppression with a decrease in the number of white blood cells below 700 in μl. Do not take aspirin for 4 weeks. After vaccination (risk of Ray's syndrome). The vaccine virus does not cause generalized pustules in patients with atopic eczema.

Post-exposure prophylaxis of varicella

With the introduction of the vaccine Varilrix in the first 96 hours after contact, a 90% protective effect is achieved. With pronounced immunosuppression, contact persons are injected with human immunoglobulin for iv administration, acyclovir is prescribed.