2 doses of flu vaccine reduce disease burden

Every flu season, many children get the flu shot. The yearly recommendations for the vaccine state that children should receive 2 doses during their first vaccination season. A new study in JAMA Pediatrics looks at whether improving adherence to the initial 2-dose series could reduce the burden of influenza in young children, one of the most vulnerable populations for the disease.¹

Investigators conducted this test-negative case-control study in outpatient clinics and emergency departments during the 4 influenza seasons from 2014-2015 through 2017-2018. Children were aged 6 months to 8 years and presented to outpatient care within 7 days of onset of acute respiratory tract illness with cough. Each child was tested with real-time, reverse-transcriptase polymerase chain reaction (PCR) for influenza.

The sample included 7533 children. In the enrollment season, 3912 children were unvaccinated; 2924 children were fully vaccinated; and 697 were partially vaccinated. The adjusted vaccine effectiveness against any influenza was 51% in fully vaccinated children and 41% in partially vaccinated children. Among the 1519 vaccine-naïve children aged 6 months to 2 years, the vaccine effectiveness for 2 doses in the enrollment season was 53% and 23% for 1 dose. Children who had 2 doses were found to be less likely to test positive for influenza when compared with children who only had 1 dose.

The researchers concluded that children who received the recommended number of doses, which was consistent with current vaccine policy, saw higher vaccine effectiveness than children who only received partial vaccination in all 4 influenza seasons studied. 

References:

1.    Chung JR, Flannery B, Gaglani M, et al. Patterns of influenza vaccination and vaccine effectiveness among young US children who receive outpatient care for acute respiratory tract illness. JAMA Pediatr. May 4, 2020. Epub ahead of print. doi: 10.1001/jamapediatrics.2020.0372