Vaccine Schedules Gregory Hussey Vaccines for Africa Initiative Institute of Infectious Diseases University of Cape Town www.vacfa.com gregory.hussey@uct.ac.za
Expanded Programme on Immunization (EPI) • Established 1974 • Built on advances in smallpox eradication • Objective to raise childhood immunization coverage. • Basic vaccines – BCG, OPV, DTP, Measles. • Strategy – routine immunization services.
Five operational components of EPI Vaccine supply & Logistics quality Service delivery Advocacy & Surveillance communication
Supporting elements of the EPI Elements exist at national, regional and district level Political and social commitment Actions of development partners
Estimated Lowest Price* to purchase a full course of vaccines for a child up to 1 year of age, according to WHO Universal Recommendations^ $40.00 6) PCV Purchased $35.78 by GAVI $35.00 5) Rotavirus $30.00 Cost of following WHO $27.16 recommendations is rising! $25.00 USD $20.00 3) Hib 4) PCV $15.00 $11.11 $11.58 $11.04 $10.00 1) Traditional 2) Hepatitis B EPI $5.00 $2.39 $2.23 $1.37 $1.40 $1.26 $0.00 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Year MSF – The right shot
Vaccine costs for SA • BCG R4 • OPV R2 • Measles R8 • Hep B R16 • Hib /DTP/IPV R408 • Rota R160 • Pneumo R510 • HPV R700 • TOTAL R1808
What is “ routine immunization ” • No standard definition – Means different things to different people – Regional and agency differences • The sum of human and logistical activities or events to ensure the regular delivery & uptake of vaccines & the monitoring and evaluation of their impact
What is “ routine immunization ” • Implies the “ regular ” delivery, i.e. a known schedule of EPI vaccines • Part of a larger plan • Not time limited • Goal to provide needed vaccines to all eligible persons and to successive birth cohorts
Routine vs Supplemental immunization Routine: Day to day immunisation according to country immunisation schedule Supplemental: In addition to/adding to routine/ strengthening routine immunisation coverage
Service delivery • Vertical service with centralized leadership and management, supervision, training and M&E • Part of comprehensive primary care with or without central procurement, training and M&E
Specific strategies for delivery • Fixed clinics – periodic or continuous • Outreach – fixed site or door-to-door visits • Mobile teams usually from a fixed clinic • Supplementary immunization activities such as campaigns
Factors that may influence seroprotection rates following vaccination • Age – elderly and very young / premature infants • Immune deficiency • Genetic factors • Dose of vaccine • Migrants • Nutritional status – malnourished / vitamin A deficient • Route of administration – id vs im
http://www.who.int/immunization/policy/imm unization_tables/en/
Basic schedule – DTP based
Vaccination of Premature infants • The immune response to vaccination is a function of postnatal rather than gestational age. Transplacentally acquired maternal antibody is present in lower concentrations in prems and persists for shorter period. • Infants born prematurely, regardless of birth weight, should be vaccinated at the same chronological age and according to the same schedule and precautions as full-term infants and children. • Exception: HBV - Decreased seroconversion rates might occur among certain preterm infants with birth weights of less than 2,000 g after administration of hepatitis B vaccine at birth. DON ’ T COUNT HBV1 DOSE. • Several studies suggest that the incidence of adverse events after vaccination of preterm infants is the same as or lower than that of full-term infants vaccinated at the same chronological age.
Vaccination of ill infants • Mild illness is not a contra-indication for vaccination. • Postponing vaccination in children with minor febrile or afebrile illness constitutes a missed opportunity to protect a child from disease, can contribute to outbreaks of vaccine- preventable disease. • Vaccination usually is deferred in persons who have moderate or severe illness.
Conclusion Immunisation is an evolving science Vaccination schedules are not set in stone. Given the differences in epidemiology, health infrastructure and resources, it will be difficult to develop a single immunisation schedule for all countries. Optimising schedules for new vaccines could reduce cost and streamline their integration with other vaccines. WHO has recommended vaccination schedules; they are very useful, particularly in low- and middle-income countries.
Seroconversion • Seroconversion is the development of detectable specific antibodies to microorganisms in the blood serum as a result of infection or immunization. Serology (the testing for antibodies) is used to determine antibody positivity. Prior to seroconversion, the blood test is seronegative for the antibody; after seroconversion, the blood test is seropositive for the antibody. • Seroconversion usually means that you have developed immunity to the specific infection. HOWEVER • seroconversion may indicate current infection – and transmissibility of a pathogen – eg, HIV-1 – seroconversion to p24 and/or p41 antibody production or HBV – seroconversion to surface antibody-HBsAb or e antibody – HBeAb production.
Seroprotection • the level of antibody titers equal or above which you are regarded as being protected from disease. • seroprotection rates refer to the % of infants with antibody titers equal or above the assay cut-off were set such that subjects who had titers above the cut off could be considered protected from disease.
Correlate of protection • Correlates of immunity/protection to a virus or other infectious pathogen are measurable signs that a person (or other potential host) is immune, in the sense of being protected against becoming infected and/or developing disease. • For many viruses, antibodies serve as a correlate of immunity. So for example, pregnant women are routinely screened in the UK for rubella antibodies to confirm their immunity to this infection which can cause serious congenital abnormalities. • In contrast for HIV, TB, HPV, Malaria, the simple presence of antibodies is clearly not a correlate of immunity/protection since infected individuals develop antibodies without being protected against disease. • The fact that the correlates of immunity/protection remain unclear is a significant barrier to HIV vaccine research. There is evidence that some highly exposed individuals can develop resistance to HIV infection, suggesting that immunity and therefore a vaccine is possible. However, without knowing the correlates of immunity, scientists cannot know exactly what sort of immune response a vaccine would need to stimulate, and the only method of assessing vaccine effectiveness will be through large phase III trials with clinical outcomes (i.e. infection and/or disease, not just laboratory markers).
Vaccines and Related Biological Products Advisory Committee March 7, 2001 FDA Briefing Document for SmithKline Beecham Biologicals’ DTPa-HepB-IPV Vaccine Antigen Serological Method Endpoints** DTPa-HepB-IPV antigens Diphtheria Toxoid (D) ELISA 0.1 IU/mL Tetanus Toxoid (T) ELISA 0.1 IU/mL Pertussis Toxoid (PT) ELISA 5 EL.U/mL Filamentous Haemagglutinin (FHA) ELISA 5 EL.U/mL Pertactin (PRN) ELISA 5 EL.U/mL Hepatitis B surface antigen (HBs) RIA 10 mIU/mL Poliovirus types 1, 2, 3 (IPV) Cell culture Neutralization 1/8 Haemophilus influenzae type b (Hib) ELISA* 0.15 and 1.0 mcg/mL
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