Differences in Seasonal and H1N1 Influenza Vaccine Acceptance Among Healthcare Workers Serving Immunosuppressed Patients During the nH1N1 Pandemic

Background: The NIH Clinical Center (CC) is a 234-bed clinical research hospital with a patient population that is largely immunosuppressed and highly vulnerable to viral respiratory infections. In 2008, the CC mandated that all staff with patient contact be vaccinated or formally decline vaccination against influenza. The 2009-10 influenza season marks the second year of mandatory influenza immunization, and included both seasonal and novel H1N1 (nH1N1) vaccines. The electronic system used the previous year to facilitate tracking of compliance was modified to accommodate both vaccines. 

Objective:  To evaluate the acceptance of two vaccines in a mandatory influenza vaccination campaign.

Methods:  Using a departmental questionnaire, we generated a database of staff with patient contact, including NIH employees and contract staff. The software tracked compliance for each vaccine, using identification numbers magnetically encoded on employee identification badges. Vaccination with seasonal and nH1N1 vaccines was staggered due to the shortage of nH1N1 vaccine during the campaign's first two months. Reminders to workers and compliance reports to supervisors were sent via electronic mail. After staff members presented for immunization, the electronic system automatically sent them documentation of receipt of each vaccine.

Results:  Among 3643 staff members with patient contact, 3408 (93.6%) had complied with the policy by the 3rd week of January. Among the compliant, 2940 (86.2%) received the seasonal influenza vaccine and 2810 (82.5%) received the nH1N1 influenza vaccine. Significantly more staff (521; 14.6%) declined nH1N1 vaccination than declined seasonal influenza vaccination (395; 11.8%; p<0.0001). The most common reasons for declination of both vaccines were ‘other,' fear of side effects, and a belief that there was a low risk of acquiring influenza infection. For each vaccine, 2.2% claimed a medical contraindication to vaccination. The ‘other' and ‘concern about side effects' reasons for declining nH1N1 vaccine were significantly greater than for seasonal vaccine (p<0.0001 for both). At the same point during the 2008-09 campaign, a higher proportion of workers had been vaccinated (88.9%; p=0.002), and significantly fewer had declined vaccination (9.7%; p=0.02).

Conclusions:  Despite the added challenges of a second influenza vaccine and limited nH1N1 vaccine availability, the mandatory influenza vaccination campaign was successful in its second year, with at least 81% and 78% of health care workers without contraindications receiving seasonal and nH1N1 vaccines, respectively. The electronic tracking system facilitated simultaneous monitoring of compliance with each vaccine. The campaign will continue over the coming weeks until it has achieved 100% compliance.