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Influenza Vaccination Among Two Year Olds in a Population-

Based SurveyKenneth D. Rosenberg, MD, MPH

Alfredo P. Sandoval, MS, MBAOregon Public Health Division, Office of Family Health,

Portland, OR

Oregon Public Health Association annual meeting

October 19, 2010

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Overview of presentation

• Flu vaccination of children is relatively new• Flu vaccination of children is the best way to

decrease flu morbidity and mortality for elderly• When flu vaccine is in provider offices:

– Providers vaccinate children who are in for routine care

– Providers don’t reach out to other children

• We need new strategies to increase flu vaccination of children: – Provider-based– School-based– Community-based

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Background: Flu vaccination for children

• In 1982, the American Academy of Pediatrics recommended influenza vaccination for high risk children but not for non high-risk children.

• In 2004, the Advisory Committee of Immunization Practices (ACIP) recommended routine immunization vaccination for all children 6-23 months old.

• In 2006, ACIP expanded the recommendation to include all children 24-59 months old.

• In 2009, ACIP: all children aged 6 months through 18 years should be vaccinated against influenza every year.

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Background: Why flu vaccination for children?

• Influenza causes morbidity and mortality children.

• Main reason for flu vaccination of children is to decrease flu morbidity and mortality for other at-risk community members including those who are elderly and disabled. – Elderly people are less able to generate a robust

immune response to flu vaccination than children.– Flu vaccination of children disrupts the epidemic

spread of flu through children in communities

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Background: Michigan experiment

• In 1970, Monto et al. reported on 2 neighboring Michigan communities: – One: 85% of school children got flu vaccine– Other: school children were not vaccinated

• The community with vaccination of school children had one third as much influenza-like illness among adults.

• Reference: Monto AS, Davenport FM, Napier JA, Francis T Jr. Modification of an outbreak of influenza in Tecumseh, Michigan by vaccination of schoolchildren. J Infect Dis. 1970;122:16-25.

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Background: Japan experience

• Most Japanese schoolchildren were vaccinated against influenza from 1962 through 1987.

• Vaccination was mandatory, then laws were relaxed in 1987 and repealed in 1994; subsequently, vaccination rates dropped to low levels.

• After the vaccination of schoolchildren was discontinued, the excess mortality rates and the excess mortality from pneumonia and influenza in Japan increased.

• They concluded that vaccinating schoolchildren against influenza decreased morbidity and mortality for older persons.

• Reference: Reichert TA, Sugaya N, Fedson DS, Glezen WP, Simonsen L, Tashiro M. The

Japanese experience with vaccinating schoolchildren against influenza. N Engl J Med. 2001;344:889-96.

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Background: U.S. estimates

• In 2005, Weyker et al. estimated the population-wide benefits of routine flu vaccination of U.S. children (ages 6 months to 18 years).

• They found that– vaccination of 20% of children would reduce the

total number of influenza cases in the U.S. by 46% – Vaccination of 80% of children would reduce the total

number of cases by 91%.

• Reference: Weycker D, Edelsberg J, Halloran ME, Longini IM Jr, Nizam A, Ciuryla V, Oster G. Population-wide benefits of routine vaccination of children against influenza. Vaccine. 2005;23:1284-93.

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Background: Day Care• A randomized control trial of US Naval personnel

found that vaccinating day care children against influenza helped reduce influenza-related morbidity among their household contacts, particularly among school-aged contacts.

• The authors concluded that “Our results suggest that during…pandemics, vaccination programs targeting day care children may be one effective strategy to reduce influenza transmission in households and perhaps communities.”

• Reference: Hurwitz ES, Haber M, Chang A, Shope T, Teo S, Ginsberg M, Waecker N, Cox NJ. Effectiveness of influenza vaccination of day care children in reducing influenza-related morbidity among household contacts. JAMA. 2000;284:1677-82.

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Background: Hypotheses

We hypothesized that:

(1) most children receive flu vaccination if they are in provider offices when flu vaccine is available and

(2) that children who are not normally in the providers’ offices are not routinely being encouraged to come to the office to receive the vaccine.

We tested this hypothesis by looking at whether two- year- olds had received flu vaccination in the past year.

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Methods: PRAMS/PRAMS-2

3 linked data sets: – Oregon Pregnancy Risk Assessment

Monitoring Survey (PRAMS) 2004-2005– Oregon PRAMS-2 (its longitudinal follow up)– associated birth certificates.

Among children born 2004-2005: – 1,911 respondents to PRAMS-2 – weighted response rate was 56.6%.

In the PRAMS-2 survey: mothers were asked whether their two-year-old had a flu shot anytime during this year’s flu season.

Methods: PRAMS/PRAMS-2

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Results• 37.5% of mothers reported that

their two year old child had had a flu vaccination in the past year.

• Two-year-olds were more likely to have received flu vaccination if their birthday was in November, December or January than if their birthday was in July, August or September (table).

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Table. Proportion of two year old children who received influenza vaccination by month of

birth, weighted percent• Birth month Got influenza vaccination % (wtd)• January 2004 47.6• February 2004 45.5• March 2004 38.9• April 2004 49.9• May 2004 58.2• June 2004 38.6• July 2004 22.5• Aug 2004 14.4• Sept 2004 26.4• October 2004 27.7• Nov 2004 45.6• Dec 2004 47.1• TOTAL 2004 38.2

• January 2005 50.7• February 2005 30.1• March 2005 46.1• April 2005 36.2• May 2005 42.4• June 2005 36.5• July 2005 15.2• Aug 2005 15.9• Sept 2005 11.0• October 2005 38.1• Nov 2005 58.8• Dec 2005 51.7• TOTAL 2005 36.9

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Discussion: 2-year well child care visit

Two-year-olds were more likely to have received flu vaccination if their birthday was in November, December or January

We believe that this is because most two-year-olds are in their provider’s office for a routine two-year-old well child care visit when the child is 24-25 months old.

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Discussion: hypothesesWe explored 2 hypotheses:

(1) most children receive flu vaccination if they are in provider offices when flu vaccine is available and

(2)that children who are not normally in the providers’ offices are not routinely being encouraged to come to the office to receive the vaccine.

These hypotheses appear to be true.

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Discussion: increase office-based flu

vaccinationThere are two ways in which flu vaccination can be increased for children:

(1) all eligible children who are in the office should be vaccinated when providers have vaccine in their office; and (2) systems are needed to vaccinate children who would not normally be in providers’ offices at the time when the office has vaccine.

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Conclusion

What happens to two year olds is probably similar to what happens to all children:

– they are likely to get flu vaccination if they are in the office when vaccine is available

– they are not likely to get flu vaccination if they are not in the office when vaccine is available.

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Conclusion3 strategies for increasing flu vaccination of children:• PROVIDER-BASED STRATEGIES: they are already set up

(but many families lack coverage and many offices have limited excess capacity).

• SCHOOL-BASED STRATEGIES: most children attend school or preschool (although many of the youngest children do not).

• COMMUNITY-BASED STRATEGIES: rudimentary systems (LIKE MASS VACCINATORS) already exist -- mostly for providing influenza vaccine to the elderly.

• These strategies are not mutually exclusive. • All three strategies should be pursued, at least in the

early period of planning to increase influenza vaccination of children.

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