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Long-Term Effectiveness of Varicella Vaccine.pptx
- 1. Dr. M Zain ul Abadin PGR-1 Peads unit-2
- 2. PEDIATRICS, the official journal of the American Academy of Pediatrics. Title:Long-term Effectiveness of Varicella Vaccine: A 14-Year, Prospective Cohort Study conducted at multiple sites in Kaiser Permanente Northern California (KPNC) Roger Baxter, Paula Ray, Trung N. Tran, Steve Black, Henry R. Shinefield, Paul M. Coplan, Edwin Lewis, Bruce Fireman and Patricia Saddier, originally published online April 1, 2013
- 3. Varicella commonly known as chicken pox is a highly contagious disease caused by the initial infection with varicella zoster virus characterized by vesicular rash.
- 4. Varicella vaccine is a live attenuated vaccine for active immunization for the prevention of varicella in individuals 12 months of age or older. Each dose is approximately 0.5 mL and is administered by subcutaneous injection. Children (12 months to 12 years of age): If a second dose is administered, there should be a minimum interval of 4 months between doses.
- 5. Most cases of chickenpox are relatively mild and run their course in five to 10 days. It can be very serious, even life-threatening, in a small percentage of people. Before the varicella vaccine was licensed in the U.S. in 1995, there were approximately 100 deaths and more than 11,000 hospitalizations a year from chickenpox. Most of the people who died were healthy before they got chickenpox.
- 6. WHAT’S KNOWN ON THIS SUBJECT: Varicella vaccine is known to be highly effective, with added benefit from a second dose. WHAT THIS STUDY ADDS: the lasting effectiveness of varicella vaccine and the benefit of the second dose. Breakthrough varicella occurred soon after vaccination varicella rates did not increase over 14 years, and there was no increase in zoster in the cohort.
- 7. Varicella vaccine was licensed in the United States in 1995 for children 12 months of age. A second dose was recommended in the United States in June 2006. Varicella incidence and vaccine effectiveness were assessed in a 14-year prospective study conducted at Kaiser Permanente Northern California.
- 8. A total of 7585 children vaccinated with varicella vaccine in their second year of life in 1995 were followed up prospectively for breakthrough varicella and herpes zoster (HZ) through 2009. A total of 2826 of these children received a second dose in 2006–2009. Incidences of varicella and HZ were estimated and compared with prevaccine era rates.
- 9. In this cohort of vaccinated children, the average incidence of varicella was 15.9 per 1000 person- years, nine- to tenfold lower than in the prevaccine era. Vaccine effectiveness at the end of the study period was 90%, with no indication of waning over time. Most cases of varicella were mild and occurred early after vaccination. No child developed varicella after a second dose. HZ cases were mild, and rates were lower in the cohort of vaccinated children than in unvaccinated children during the prevaccine era.
- 13. The largest and longest follow-up study of varicella vaccine, with 14 years of active surveillance. The incidence rate of varicella was 9 to 10 times lower than rates in unvaccinated children of the same age in the prevaccine era. Shows vaccine effectiveness of >90% The incidence rate of breakthrough varicella steadily decreased over time,and no increase was observed during the 14 years of follow- up.
- 14. Few breakthrough cases were severe (only 28 of 7585 children) Prevention of moderate to severe disease was achieved with 1 dose of varicella vaccine. Most breakthrough cases occurred in the early years of the study. No breakthrough varicella was reported after the receipt of a second dose of varicella vaccine. Incidence rate of HZ among vaccinated children may be lower than after naturally acquired varicella in unvaccinated children of the same age.
- 15. Incidence rates of breakthrough varicella per 1000 PY (first episode only), according to calendar year, since vaccination in 1995.
- 16. Breakthrough varicella cases were based on parental report that may have been underreported or overreported. Although parental reports of varicella have been shown to be reliable for young children,in adolescents it may be less reliable. Comparisons of current rates of varicella and zoster versus published historical rates may be problematic because of some possible changes over time in disease incidence and case ascertainment, and potential differences in underlying populations.
- 17. This study confirmed that varicella vaccine is effective at preventing chicken pox, with no waning noted over a 14-year period. One dose provided excellent protection against moderate to severe disease, and most cases occurred shortly after the cohort was vaccinated. The study data also suggest that varicella vaccination may reduce the risks of HZ in vaccinated children than in the prevaccine era.