Vaccine Schedules Gregory Hussey Vaccines for Africa Initiative - PowerPoint PPT Presentation

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