629

Young Child Immunization Survey

Los Angeles, CA

Summer, 1997

A collaborative effort of UCLA and the Immunization Program Office of the Los Angeles County Department of Health Services

629

630630

631

Survey of Children, Aged 2-3 YearsThree Zip Code Areas of Los Angeles County

Zip code areas 90007, 90011 and 90015 near downtown Los Angeles

90007

90011

90015

110

110

10

10

631

632

How the Survey was Conducted

• Face-to-face Interviews of parents of 271 children, aged 2-3 years

sampled from an enumeration list of all eligible children in three central Los Angeles zip code areas

• The margin of sampling error for all children is plus or minus 4-5 percentage points

for certain subgroups the error margin may be somewhat higher

• Most of the interviews were completed during four weekends between July 12 and August 3, 1997

conducted by volunteers, UCLA students and Immunization Program staff

632

633

Sampling Scheme for Two-stage Cluster Survey

Study Population

First stage sampling of

clusters

Second stage sampling of

persons

633

634

Select the Sample

• Randomly select 30 clusters with probability proportionate to estimated size (PPS)

based on the 2-3 year-old population in the 1990 Census

• Identify the study area Zip codes 90007, 90011, 90015

• Divide the study area into clusters (i.e., groups of blocks )

Each area has 20 or more children, aged 2-3 years

634

635635

Area is divided into

clusters (i.e., group of blocks)

636

Steps for Probability Proportionate to Size (PPS) Sampling at First Stageand Simple Random (SR) Sampling at Second Stage

(A) (B) (C)

6,000

5,000

4,000

3,000

2,000

1,000

0

(D) (E) (F)

4

5

3

2

1

(G)

PPS

PPS

PPS

PPS

PPS

SR

SR

SR

SR

SR

636

637637

30 clusters are selected with

probability proportionate to

estimated size (PPS)

638

Create a Map for Each Cluster

• Created with a computer programShows blocks and streets

Example with two blocks in

Cluster 22Cluster 22A Cluster 22B

Map

le

San

Ped

ro

Trin

ity

35th Street

36th Street

638

639639

Computer generated

maps

640

Create an Enumeration Form for Each Cluster

• Created with a computer programLists streets to be visited and disposition of each house that is visited

Used to identify addresses of

households with eligible children

Cluster 22A

Address and disposition

640

641

• Volunteers, UCLA students and Immunization Program staff

one member of each enumeration team had to speak Spanish

• Need to visit homes in sampled areas to find all eligible children, aged 2-3 years

know how to use map

Train Persons for Enumeration

know how to use disposition form

know how to talk to people

641

642642

Training of enumerators

643

Field VisitsYoung Child Immunization Survey

*Volunteers, UCLA students and Immunization Program staff

Enumeration weekend*Interview weekend*Clean-up days**

**Immunization Program staff

July

August

SUN TUEMON WED THU FRI SAT

13 14 15 16 17 18 19

20 21 22 23 24 25 26

27 28 29 30 31

1 2 3 4 5

6 7 8 9 10 11 12

SUN TUEMON WED THU FRI SAT

1 2

3 4 5 6 7 8 9

10 11 12 13 14 15 16

17 18 19 20 21 22 23

24 25 26 27 28 29 30

31

643

644

Enumeration WeekendYoung Child Immunization Survey

• Met at Immunization Program office and received enumeration team assignment

• At least one Spanish speaker and one driver in each team

• Work schedule was 9 am to 2 pm on Saturday and 1 pm to 4 pm on Sunday

644

645645

Morning assembly of enumerators waiting to be

assigned

646646

Assignment of

enumeration teams

647647

Two teams made up of community

volunteers and UCLA students

648648

Enumeratorsmaking house

calls

649649

Check mailboxes to determine if households are occupied

650

Reassignment of ClustersYoung Child Immunization Survey

• Three clusters were re-selected and reassigned

too few eligible children in the cluster

vacant houses or conversion of houses to businesses since time of 1990 Census

650

651651

Condemned public

housing site

652652

Former apartments converted to

garment factory

653

Sampling Eligible ChildrenYoung Child Immunization Survey

• Random selection of 10 eligible children from the enumerated list in each cluster

653

654

Interview WeekendYoung Child Immunization Survey

• Met at Immunization Program office and received interview team assignment

• Content of interview

At least one Spanish speaker and one driver in each team

Demographic characteristics

Review of immunization card

Insurance coverage

WIC participation

654

655655

Organizing interviewers

656656

Assigning interviewers to

teams

657657

An interview team with a Spanish-speaking

community volunteer and a UCLA student

658658

Abstraction of the immunization card in the

home by an interview team

659

Special Research ComponentYoung Child Immunization Survey

• Collection of saliva specimen for determining immunity to measles virus

• Laboratory analysis in England**

Look for presence of IgG antibodies against measles in saliva

Radioimmunoassay technique

Previously evaluated in Immunization Project pilot study

Collected with Omni-Sal* saliva collection device

* Saliva Diagnostic Systems, Inc., Vancouver, Washington, USA** Central Public Health Laboratory, London, England 659

660660

Child shown instruction card with two heads to aid

with saliva collection

661661

Saturation of cotton pad with 1 milliliter of saliva

662662

Father as respondent

with son

663

ParticipationYoung Child Immunization Survey

Visited HH =

Enumerated children* =

Sampled children =

At home children** =

Interviewed children =

SampledchildrenAt homechildren

0 20 40 60 80 100Percent of Sampled Population

Participation (%)

271

333

429

719

5,300

7 8 9 10 11Interviewed Children per Cluster

02468

10121416

Interviewed Children Per Cluster

Number of Clusters

* up to two visits per HH** up to three visits per sampled child

663

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Telephone Status of HouseholdsYoung Child Immunization Survey (n=271)

Home phone73%

No home phone*25%

Only work phone

2%

* Homes without telephones would have been excluded if done as a random-digit dial telephone survey

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