The Risks for Varicella Vaccine Refusal

From Medscape Pediatrics > Viewpoints
William T. Basco, Jr., MD

Arch Pediatr Adolesc Med. 2010;164:66-70

Study Summary
The investigators noted that parental refusal of vaccination is an increasing problem, owing to a combination of concern over vaccine safety combined with a belief that children are at low risk for infection because of fewer vaccine-related illnesses in the United States. Varicella, perceived as a less serious illness by parents compared with other vaccine-preventable diseases, appears to be the most commonly refused vaccine.

This study used Kaiser Permanente data from Colorado over a 10-year period to determine the risk for varicella in nonimmunized children who were 1-12 years old. The investigators searched clinical databases for patients with a diagnosis of varicella or any tests ordered to diagnose varicella. After identifying potential cases, the research team reviewed the individual records to determine symptoms; physical findings; laboratory evaluation results; and other clinical outcomes, including complications from varicella, such as impetigo or cellulitis. The chart review included searching for contacts from whom the child may have contracted varicella. Children were considered "cases" if they were diagnosed with varicella by a physician. After identifying cases, the investigators matched them to 4 controls each on the basis of age, sex, and length of enrollment in the health plan.

After matching cases and controls, a different abstractor reviewed vaccination status, noting whether children had received the varicella vaccine at least 14 days before their varicella infection. Only children who were unvaccinated and who had vaccine refusal documented in their charts were considered vaccine refusers. Children who were unvaccinated, but for whom the reason for nonvaccination could not be determined, were excluded. Among 86,000 children screened for inclusion, the investigators identified 133 who had varicella and complete data. These patients were matched to 493 controls.

Among all cases and controls, only 10 children were vaccine refusers, and 7 of them contracted varicella, for a varicella infection frequency of 70% among vaccine refusers. Vaccine refusers were overrepresented in the cases, comprising 5.3% of cases compared with only 0.6% of controls.
Refusal of vaccine greatly increased the odds that a child would contract varicella (odds ratio 8.6, 95% confidence interval 2.2-33.3). By calculating the attributable risk, the investigators determined that all 7 of the varicella infections among vaccine refusers were related to vaccine refusal.
For the total population, the investigators estimated that 4.7% of all varicella cases were a consequence of vaccine refusal. Just under 5% (4.5%) of the cases of varicella experienced bacterial infection, with 1.5% developing cellulitis.

The study authors concluded that children whose parents refuse varicella vaccination are at high risk of contracting varicella.

Viewpoint
The study authors pointed out that the greatest advantage of this study is perhaps the data that it provides for discussions between families and providers about vaccine concerns. Given all of the media coverage of vaccine concerns, these discussions likely are happening more frequently now than at any time in the recent past.
The economic argument around universal vaccination for varicella hinged mainly on the savings from less parental missed work, and that may be a more difficult argument to make with some parents.
However, mild morbidities from varicella infection are common; furthermore, refusal of varicella opens up a slippery slope that may encourage parents to consider skipping other vaccines. Reassurance by a trusted healthcare provider, with data to back up these discussions, is perhaps the best way to encourage parents not to let slip our substantial progress in preventing infectious diseases.