La vaccination universelle contre la grippe Allison McGeer, MSc, MD Mount Sinai Hospital, Toronto 6 es Journées annuelles de santé publique Évaluation des technologies et prise de décision en vaccination Québec, 20 novembre 2002 www.inspq.qc.ca/jasp
Myth #1 We shouldn t consider universal vaccination because: Influenza is not a severe disease
Influenza is not by any means so severe or so rapidly fatal a disease as cholera, but the mortality which it has produced is greater, as it affects almost every person in society, while the ravages of cholera are comparatively limited. Robert Graves, 1848
Influenza Every year 5 million Canadians (1 in 6) will be infected 50,000 will be hospitalized (1:100 >65 yrs) 3,000 people will die 7% of 2-6 yr olds will have acute otitis media 1.5 million work-days will be lost
Excess rates of hospitalization due to influenza in children Age group Admissions per 1000 children/ year Neuzil et al. 0-1 yr 7.6 1-4 yr 1.9 5-15 yr 0.4 Izurieta et al 0-1 yr 2.1 2-4 yr 0.44 5-17 yr 0.07
Hospitalizations for acute respiratory illness in children Rate per 10,000 person-months 300 250 200 150 100 50 0 <2 years 2-4 years Flu RSV Summer
Illness in childhood HSC review of encephalitis 94/5-2 cases of influenza A associated disease (both with late deficits) 95-99 - 20 cases associated with influenza CHEO 4 cases nosocomial influenza/yr, 95-99 16% requiring ICU admission, median extension of LOS 5.5 days (range 2-16 days)
Myth #2 We shouldn t consider universal vaccination because: we re guessing every year about strains it prevents only a minority of influenza-like illness (ie. only that due to influenza) it doesn t prevent all influenza
Similarity of Laboratory Confirmed Influenza Infections with Vaccine Antigens, Canada 0 20 40 60 80 100 80/81 81/82 82/83 83/84 84/85 85/86 86/87 87/88 88/89 89/90 90/91 91/92 92/93 93/94 94/95 95/96 96/97 97/98 98/99 99/00 00/01 01/02 Percent of strains related to vaccine antigen Influenza Season Solid line shows smoothed trend line for the overall percentage match between 1980/1 and 2001/2
Does conjugate meningococcal vaccine protect against all meningitis? all meningococcal meningitis? Does pertussis vaccine protect against all prolonged cough illness? Does this mean these vaccines aren t important or useful?
Myth #3 We shouldn t consider universal vaccination because: it isn t feasible to deliver annual vaccine to that many people
Recommendations for influenza vaccination Population group Size Cumulative proportion >=65 yrs of age 3,989,169 13% chronic illness: 15-64 2-15 2,593,927 464,700 22% Household contacts high risk 3,058,627 32% Health care workers 1,268,380 36% 50-65 yr olds 5,221,126 53% 6mo-2 yr olds 511,594 54%
Ontario program Announced late July 2000 Implemented October 2000 Overall, 44% of Ontario population vaccinated in first year
Why universal vaccine?
Reasons Achieve vaccine targets in high risk groups Reduce illness in healthy adults and children Provide herd immunity
Influenza Vaccination Rates, Community Percent vaccinated 70 60 50 40 30 20 10 NS PQ ON MB 0 >=65 yrs of age <65, with chronic illness
Influenza vaccination rates, by risk group, Toronto Cumulative percent of population group vaccinated 80 70 60 50 40 30 20 10 0 1997 1999 2001 <65, ill >64, well >64, ill
Influenza vaccination rates, by risk group, Toronto Cumulative percent of population group vaccinated 90 80 70 60 50 40 1997 1999 2001 <65, ill >64, well >64, ill
Reasons Achieve vaccine targets in high risk groups Reduce illness in healthy adults and children Provide herd immunity
Effectiveness of influenza vaccine in healthy adults Reductions associated with vaccine Inactivated Cold-passaged Episodes URI 25% 24% Days missed 43% 29% work Provider visits 44% 41% Antibiotic days - 46% Nichol et al. NEJM 1995;333: 889-93
During the Canadian Consensus conference on pertussis, participants agreed that the goal of pertussis control strategy is to decrease the morbidity and mortality of pertussis across the entire lifespan. It was further agreed that protection of adolescents and adults is a worthy goal for the benefit of these cohorts themselves and whatever the collateral benefit of protection to infants. These goals are fully endorsed by NACI. From the Canadian Consensus Conference Statement on Pertussis Vaccine, 2002
Morbidity in healthy adolescents/adults Per 1000 persons/yr Pertussis Influenza Incidence 3.4 60 Days missed work 17 100 Days symptomatic 142 210
Benefit/cost ratio, vaccination of healthy adults Study All benefit/cost ratio Medical care benefit/cost rat Kumpulainen,1997.07.02 Bridges, 2000.55.35 Riddiough, 1983.68.35 Nichol, 2001 1.8.38 Campbell, 1997 2.0.72 Burkel, 1999 2.5.40 Smith, 1979 2.7 - Levy, 1996 2.7.15 Yassi, 1991 2.9 - Nichol,1995 3.5 1.6 Leighton, 1996 3.6 - Muennig, 2001-1.2
Intranasal influenza vaccine in children (Belshe( Belshe,, NEJM, 1998) Placebo Vaccine Protective efficacy Influenza 18% 1.3% 93% Influenza with fever Febrile otitis media 15% 0.7% >95% 20% 14% 30%
Reasons Achieve vaccine targets in high risk groups Reduce illness in healthy adults and children Provide herd immunity
Haemophilus influenzae,, type b, Ontario, 1980-1996 1996 300 250 200 PS licensed PS 2 yrs Conj 18mos 150 100 PS licensed 50 0 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
Haemophilus influenzae,, type b, Ontario, 1980-1996 1996 160 140 120 100 80 60 40 20 0 PS licensed PS 2 yrs Conj 18mos PS licensed 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
Effectiveness of vaccination of daycare children in reducing illness among household contacts All respiratory disease Febrile respiratory disease Reduction in disease in: Unvaccinated Vaccinated contacts contacts 16% 22% (P=.10) (P=0.04) 47% (P=.04) 22% (P=.38) Hurwitz, JAMA, 2000:284;1677
Mortality among patients Vaccination uptake and mortality among patients in 50 40 30 20 10 0 long term care 0 10 20 30 40 50 60 70 Vaccination rate in staff Carman et al. Lancet 2000;355:93
Relationship between LTCF staff vaccination rates and number of influenza outbreaks, Canada,1998/9 Probability of at least one influenza outbreak 60 50 40 30 20 10 0 P=0.02, MH chisquare <25% 25-50% 50-75% >75% Percentage of staff vaccinated against influenza
Why universal vaccine? It will increase protection in at risk persons by increasing vaccination rates It will reduce morbidity in healthy adults and children It is cost-saving for the former, and costeffective for the latter (without considering the impact on antibiotic use) There is likely a degree of herd immunity
No. viral isolates per 1000 population, by province and year Viral isolates per 1000 population 0.6 0.5 0.4 0.3 0.2 0.1 0 97/98 98/99 99/00 00/01 01/02 BC AB SK MB ON PQ NS