Although the safety and efficacy of infant/childhood immunizations have been proven, there are still many barriers that exist that prevent protecting vulnerable population groups from vaccine preventable diseases. These multiple barriers are currently addressed in these areas:

• economic and cultural risk factors
• provider practices
• families
• inadequate knowledge

Economic and Cultural Risk Factors

Demographic and social support variables indicate that children are at risk for many diseases. Data from the CDC National Immunization Survey indicates that children living below the poverty level and that Black and Hispanic children had immunization rates below the national average (CDC 1997). A study in Baltimore found that children of teenage mothers, children in large families, and children whose mothers lack social support systems had lower immunization rates at age two. Most of these mothers believed that immunizations protected their children from disease and that these diseases had serious consequences. However, these parents also believed that timing of immunizations did not matter (Strobino, Keane, Holt, Hughart and Guyer 1996). A study of Mexican American mothers by Guendelman, English and Chavez (1995) found that children of mothers who smoked, drank alcohol, were unaware of child safety measures, had a stressful event since birth of the child, lived in chaotic households, or were new to their neighborhood had lower immunization rates. A large study of public and private patients in Texas by Suarez, Simpon and Smith (1997) found that immunization rates for families with private insurance and those using public clinics were the same, but families with Medicaid coverage had lower immunization rates. Families receiving Aid to Families with Dependent Children (AFDC) also had lower rates. Similarly, Houseman, Butterfoss, Morrow and Rosenthal (1997) found that mothers with fewer resources found it more difficult to succeed in obtaining immunizations for their children. Other identified risk factors include low parental educational level, low socioeconomic status, inability to access appropriate transportation, nonwhite race, single parent family, lack of parental care and a late start on the immunization series (Pruitt, Kline and Kovaz 1995). Knowledge of these risk factors for inadequate immunization must be incorporated into strategies to increase rates.

Provider Practices

Policies and procedures in office settings can be barriers to timely immunization. Missed opportunities are the most significant barrier among clinicians. Many reasons are given for this (Szilagyi et al. 1996): immunization status is not evaluated at each well child and acute care visit, immunizations are not given when the need is identified, immunizations are delayed for non-valid contraindications, all vaccines needed are not given at one visit and immunizations are not provided in the absence of a complete physical exam. Watson (1996) found that 78% of a group of public and private patients did not bring an immunization record to a visit. This percentage was the same for both well and acute child care visits to a provider.

Families, Inadequate Knowledge

Focus groups conducted (Houseman et al. 1997) identified additional practice setting barriers. These were:

• Parents were unable to obtain appointments in a timely manner, with some experiencing delays of 4-6 weeks. Families in stressed households found it difficult to effectively plan that far in advance.
• There were inflexible office schedules with immunizations only being administered by appointment, during a physical exam with no weekend or evening coverage.
• The office environment was frequently non-conducive with long waits for small children in crowded waiting rooms.
• Phone access was often difficult with frequent busy signals and being left on hold for long periods of time. These were considered inconvenient by many poor households without phones.
• Attitudes of staff in offices were frequently insensitive, with many mothers from low-income families feeling that staff treated them in a condescending manner, particularly if their child was behind schedule. They also felt that they were not given adequate explanations and information.
• Personal safety concerns were expressed about the location of some clinics.
• Parents had misconceptions about the safety of vaccines and their contraindications (Table 4, Table 5). Minor and serious side effects caused some parents to delay immunizations.

Table 5:Events Reportable to the National Vaccine Injury Compensation Program Following Vaccination

Vaccine	Adverse Event	Interval from vaccination (n)
Tetanus in any combination	Anaphylaxis or anaphylactic shock	7 days
	Brachial neuritis	23 days
Pertussis in any combination	Anaphylaxis or anaphylactic shock	7 days
	Encephalopathy	7 days
Measles, mumps, rubella in any combination	Anaphylaxis or anaphylactic shock	7 days
	Encephalopathy	15 days
Rubella in any combination	Chronic arthritis	42 days
Measles in any combination in an immunodeficient recipient	Thrombocytopenic purpura	30 days
	Vaccine-strain measles viral infection	6 months
OPV	Paralytic polio or vaccine-strain polio viral infection
	- in a non-immunodeficient recipient	30 days
	- in an immunodeficient recipient	6 months
	- in a vaccine-associated community case	No limit