New immunization programs in BC to prevent rotavirus, varicella, and hepatitis A

The publicly funded rotavirus vaccine for infants at 2 and 4 months of age is the orally administered live attenuated monovalent human rotavirus vaccine Rota­rix.[1] Benefits of this vaccine over the other approved product, pentavalent human-bovine reassortant rotavirus vaccine (RotaTeq), include the two dose series and a more favorable cost-effectiveness profile.[2] 

Based on im­mu­nization registry data, about one-quarter of infants in BC do not complete their third dose of DPT-containing vaccine by 8 months of age, the age by which a rotavirus vaccine series must be completed. 

Rotavirus occurs seasonally with the peak in January through April in BC. This virus accounts for up to 40% of all childhood gastroenteritis, al­though death occurs rarely in Canada. It is estimated that in Canada between 1 in 62 and 1 in 312 children under 5 years old will require hospitalization for rotavirus, 36% of children with rotavirus will see a physician, 15% will be assessed in an emergency room, and 7% will be hospitalized. 

Rotarix vaccine efficacy against severe rotavirus gastroenteritis ranged from 85% to 96% during the first rotavirus season and 79% to 86% during the second season in prelicensure clinical trials. Efficacy is unaffected by breastfeeding. The vaccine is contraindicated in infants who have had intussusception and should not be administered in those with known or suspected immunocompromise without the advice of a specialist. 

The National Advisory Committee on Immunization now recommends a second dose of varicella vaccine for children 1 to 12 years old.[3] A second dose of varicella vaccine is added to the BC schedule at school entry (4 to 6 years of age). Mounting data indicate that a single dose does not provide durable protection. 

Both primary and secondary vaccine failure (“waning immunity”) contribute to breakthrough varicella in immunized people after the first dose. Several US outbreak epidemiologic studies suggest waning immunity, with time since vaccination as a risk factor. The annual rates of varicella increased from 1.6 cases per 1000 person years within 1 year after vaccination to 9 at 5 years and 58.2 at 9 years after vaccination.[4] 

This phenomenon may be accentuated in the post-vaccine era with limited opportunity for natural boosting. Vaccine effectiveness does not appear to be related to when in the second year of life the immunization is given. At the same time as this change, the second dose of MMR previously given at 18 months of age is moved to school entry (4 to 6 years). Starting in 2015, this will allow use of combination MMRV (measles, mumps, rubella, and varicella vaccine) at school entry.

Hepatitis A vaccine is added to the routine schedule for Aboriginal in­fants in a two-dose series at the 6- and 18-month visits, and also offered to Aboriginal children at school entry and opportunistically to Aboriginal persons aged 7 to 18 years presenting for clinical services. The incidence of acute hepatitis A has declined in BC from 12.4 per 100000 in 1996 to 0.7 per 100000 in 2009, and this decline has been attributed to publicly funded vaccination of high-risk individuals including men who have sex with men and illicit drug users.[5] 

Despite this decline, four of the five outbreaks recognized in the past 15 years have affected First Nations people living on reserve.[6,7] The largest of these four outbreaks began on Vancouver Island over a year ago and has resulted in over 85 reported cases. 

Immunization of children has successfully reduced hepatitis A incidence in other countries including the US.8 Infant and child vaccination is substantially more cost effective than adult vaccination because children facilitate transmission through efficient fecal oral spread from infected diapered children, and asymptomatic infection and communities with high rates of infection have high prevalence of immunity in adults.[9] 

Question and answer documents on all these programs can be found at http://immunizebc.ca/healthcare-professionals.

For more news and information check our websites periodically at www.bccdc.ca and www.immunizebc.ca. 
—Monika Naus, MD, MHSc
Medical Director, Immunization Programs and Vaccine 
Preventable Diseases
BC Centre for Disease Control

This article is the opinion of the BC Centre for Disease Control and has not been peer reviewed by the BCMJ Editorial Board.

References

1. National Advisory Committee on Immunization. Updated statement on the use of rotavirus vaccines. Can Commun Dis Rep 2010;36(ACS-4):1-36. Accessed 23 December 2011. www.phac-aspc.gc.ca/publicat/ccdr-rmtc/10vol36/acs-4/index-eng.php.
2. Coyle D. Cost effectiveness of infant vaccination for rotavirus in Canada. March 2011. Fisman D. Economic Effectiveness of Pediatric Rotavirus Vaccination in British Columbia. June 2012. Unpublished re­ports presented to the Canadian Immunization Committee Task Group on Rotavirus Vaccine.
3. National Advisory Committee on Immunization. Varicella vaccination two dose recommendations. Can Commun Dis Rep September 2010;
36(ACS-8):1-26. Accessed 23 Dec­ember 2011. www.phac-aspc.gc.ca/publicat/ccdr-rmtc/10vol36/acs-8/index-eng.php.
4. Chaves S, Garquillo P, Zhang JX, et al. Loss of vaccine-induced immunity to varicella over time. N Engl J Med 2007;356:1121-1129.
5. Pollock S, Sheikholeslami A, Edgar B, et al. The changing epidemiology of hepatitis A in BC: Using health authority follow-up data to inform policy and practice. Can Commun Dis Rep 2006;32:239-244.
6. BC Centre for Disease Control. Annual Summary of Reportable Diseases, various years. Accessed 23 December 2011. www.bccdc.ca/util/about/annreport/default.htm.
7. Harb J, Lem M, Fyfe M, et al. Hepatitis A in the northern interior of BC: An outbreak among members of a First Nations community. Can Commun Dis Rep 2000;26:157-161.
8. Wasley A, Samandari T, Bell BP. Incidence of hepatitis A in the United States in the era of vaccination. JAMA 2005;294:194-201.
9. Anonychuk AM, Tricco AC, Bauch CT, et al. Cost-effectiveness analyses of hepatitis A vaccine: A syste­matic review to explore the effect of methodological quality on the economic attractiveness of vaccination strategies. Pharmacoeconomics 2008;26:17-32.