Human Vaccination Against H5N1 Learning objectives Explain the - PowerPoint PPT Presentation

Human Vaccination Against H5N1

Learning objectives • Explain the indication for use of seasonal Influenza vaccination • Describe seasonal influenza vaccine composition and matching to circulating influenza strains • Describe the potential use of pandemic vaccine to limit spread • Describe the difference between the use of vaccine for seasonal epidemics versus pandemics • Monitor adverse effects of pandemic vaccine

Vaccine composition and selection

Vaccine strain selection • Annual update of vaccine strains needed due to antigenic drift of flu viruses • WHO Global Influenza Surveillance Programme established in 1948 to coordinate vaccine strain selection activities and recommendations – Global year-round virologic surveillance – Antigenic and genetic analysis – Serological studies Source: Bridges, PAHO Influenza Epidemiology Course, May 11, 2005.

WHO collaborating labs

Two main types of vaccines • Inactivated • Live, attenuated Both require – Yearly administration – Revised twice a year based on international virologic surveillance Strains most commonly grown in eggs, but also in MDCK and Vero cells. Source: Bridges, PAHO Influenza Epidemiology Course, May 11, 2005.

Influenza vaccine timetable Source: Bridges, PAHO Influenza Epidemiology Course, May 11, 2005.

Vaccine Effectiveness • Depends upon match between vaccine strain and circulating strain • 70-90% effective in preventing illness in healthy persons <65 years • Less effective for illness in elderly, but can reduce risk for hospitalization and death • Reduced vaccine effectiveness if predominant strain is antigenically drifted from vaccine strain

Influenza vaccine: number of changes 1968-2002 Source: Bridges, PAHO Influenza Epidemiology Course, May 11, 2005.

Adverse reactions Possible adverse reactions from inactivated vaccines include: • Common and immediate – Local reactions in young children – Fever – Malaise • Rare – Guillain-Barre syndrome in older adults – Facial palsy – Oculorespiratory syndrome Source: Bridges, PAHO Influenza Epidemiology Course, May 11, 2005.

Live vaccines are recommended only for healthy people aged 5-49. Contraindications for live vaccines: • Allergy to eggs • History of Guillain-Barre syndrome • <18 on long-term aspirin therapy • Pregnancy in first trimester • Immunosuppression Source: Bridges, PAHO Influenza Epidemiology Course, May 11, 2005.

Cold chain management Vaccine Vaccine manufacturer Transit storage facilities National airport (2°C-8°C) vaccine carriers based on need Transportation in refrigerated trucks, cold boxes, and/or Primary vaccine store Cold room (2°C-8°C) and freezer room (-15°C- -25°C) Intermediate vaccine store Refrigerators (2°C-8°C) Intermediate vaccine store and cold boxes and/or vaccine carries Health center Health post Recipient http://www.who.int/vaccines-access/vacman/coldchain/the_cold_chain_.htm

Seasonal Versus Pandemic Vaccines

Indications for use of seasonal vaccine

Current influenza prevention strategies • About 50 countries have government funded national influenza immunization campaigns • Recommendations vary by country, but generally involve annual immunization for: – Individuals of advanced age – Those with pre-existing chronic medical conditions – Those at increased medical risk Source: Bridges, PAHO Influenza Epidemiology Course, May 11, 2005.

Who should be vaccinated seasonally? WHO recommendations • Age – ≥ 65 or other nationally defined age limit – Residents of institutions for elderly or disabled • Occupation – Individuals with regular, frequent contact with high-risk persons (health care workers) – Individuals with frequent contact with at-risk animals (poultry farmers, cullers, etc.) • Risk Factors – Chronic conditions (Cardiovascular, Pulmonary, Metabolic, Renal, Immuno-compromised) – Pregnancy – Vulnerable population (Refugee, migrant, disaster victims) Source: Bridges, PAHO Influenza Epidemiology Course, May 11, 2005.

Vaccination of children • Children spread flu quickly due to – High attack rates – Prolonged shedding – Higher excretion of virus • The presence of a child is a risk factor for flu infection in adults (Frank et al 1985) • Immunization of 85% of school children effective in reducing severity of community outbreak in influenza A (Tecumseh, Monto, et al, 1970) • Vaccination in children may protect high-risk adults

Age recommendations in 56 countries, 2003 Source: Bridges, PAHO Influenza Epidemiology Course, May 11, 2005.

Recommendations for high-risk conditions in 56 countries, 2003 Source: Bridges, PAHO Influenza Epidemiology Course, May 11, 2005.

Recommendations for target groups in 56 countries, 2003 Source: Bridges, PAHO Influenza Epidemiology Course, May 11, 2005.

Seasonal vaccination may not be a priority • Limited data on flu occurrence and chronic diseases • Limited health care facilities and resources • Other unmet health needs which take priority

Vaccine Priorities: Seasonal vs Pandemic Influenza Seasonal Pandemic Annually recommend Initial vaccine supply will be • • vaccination for groups at much more limited high risk for severe illness & death, their close contacts, A pandemic may have • persons 50-64 years old, and impacts on functioning of HCWs the health care system and other essential services High risk includes persons • >65 years, children 6-23 months; persons with underlying chronic disease; and pregnant women

Use of vaccines in a pandemic • First line of defense in a pandemic to reduce morbidity and mortality • Contain virus close to the source

However… • Last 3 flu pandemics reached the world in 6-9 months—will spread more quickly now due to the shrinking globe • Takes approximately 4-8 months to formulate and produce vaccine • Production capabilities (100 million) are well short of what is needed • Vaccine not likely to be available before 2010 http://news.bbc.co.uk/1/hi/sci/tech/5132910.stm

Effectiveness of a pandemic vaccine may not be known until the pandemic has passed.

Goals of the Pandemic Influenza Vaccination In the likely event of a shortage given current influenza vaccine production capacity, goals of the vaccination program are to: • Decrease pandemic health impacts • Preserve critical infrastructure and minimize societal disruption

Pandemic Vaccine Purchase and Distribution • Issues to consider – Need to have manufacturers shift from annual to pandemic vaccine – Incentives for full-scale pandemic vaccine production – Local health department preferences & planning needs – Ability to effectively target doses when short supply – Equity • Plan recommends that public sector vaccine will be distributed to States for further distribution/administration • Payment or reimbursement

Vaccine Prioritization: who is vaccinated first? • Varies for each country • Plan in order to simplify the process • Example of US HHS priority recommendations WHO does not recommend mass vaccination at this time based on available data.

Vaccine Prioritization Considerations • Impact on risk of hospitalization. & death based on data from past pandemics and inter-pandemic influenza • Likelihood of response to vaccination (i.e., immunocompromised don’t respond well) • Anticipated impact of pandemic influenza on demand for healthcare and critical infrastructure, such as vaccinators and vaccine manufacturers • Current vaccine production capacity/availability • Size of prioritized groups

Example: Pandemic flu vaccine plan for United States

Recommended Vaccine Target Groups -1 Tier Group Population Percent 1A Vaccine, antiviral 40,000 .01% workers 1A Health care and public 8-9 M 3% health workers w. direct patient contact 1B >65 years with >1 high 18.2 M 6.1% risk condition* 1B 6 mos-64 yrs with >2 6.9 M 2.3% high risk conditions 1B >6 mos w. history 740,000 0.2% pneumonia/influenza hospitalization * nursing home residents excluded; see http://www.hhs.gov/pandemicflu/plan/appendixd.html

Recommended Vaccine Target Groups -2 Tier Group Population Percent 1C Pregnant women 3.0 M 1% 1C Household contacts of 2.7 M 0.9% severely immunocompromised persons* 1C Household contacts of 5.0 M 1.7% children <6 mos 1D Public health 150,000 .05% emergency response workers 1D Key government To be To be leaders determined determined * immunocompromised persons excluded; see http://www.hhs.gov/pandemicflu/plan/appendixd.html

Recommended Vaccine Target Groups -3 Tier Group Population Percent 2A Other persons at risk, 59.1 M 19.9% all ages 2B Other responders: 8.5 M 2.9% public health, public safety, utility, transportation, telecommunications, IT 3 Other key government To be <1% personnel, funeral determined directors and plus 62,000 personnel 4 Healthy persons not 179.3 M 60.4% included above For more information, see http://www.hhs.gov/pandemicflu/plan/appendixd.html

Process for monitoring for adverse reactions in a pandemic With a more widespread use of a vaccine, problems and reactions are likely to be developed that haven’t been seen before. – Enhanced reporting system – Enhanced surveillance