The US Influenza Vaccine Effectiveness (Flu VE) Network analyzed 25,019 of 42,600 outpatients aged ≥6 months enrolled within 7 days of illness-onset during six seasons from 2011-2012. Upper respiratory specimens were tested for influenza virus type and B-lineage. Using logistic regression, we estimated IIV4 or IIV3 effectiveness by comparing the odds of influenza B infection overall, and by B lineage among vaccinated versus unvaccinated participants. Over four seasons from 2013-2014, we compared relative odds of influenza B infection among IIV4 versus IIV3 recipients.
Since 2013, quadrivalent influenza vaccines containing two B viruses gradually replaced trivalent vaccines in the United States. We compared vaccine effectiveness of quadrivalent to trivalent inactivated vaccines (IIV4 to IIV3) against illness due to influenza B during the transition when IIV4 use increased rapidly.
Trivalent vaccines included the predominantly circulating B lineage in four of six seasons. During four influenza seasons when both IIV4 and IIV3 were widely used, overall effectiveness against any influenza B was 53% (95% confidence interval [CI], 45 to 59) for IIV4 versus 45% (95% CI, 34 to 54) for IIV3. IIV4 was more effective than IIV3 against the B lineage not included in IIV3, but comparative effectiveness against illness related to any influenza B favored neither vaccine valency.
Uptake of quadrivalent inactivated influenza vaccines was not associated with increased protection against any influenza B illness, despite higher effectiveness of quadrivalent vaccines against the added B virus lineage. Public health impact and cost-benefit analyses are needed globally.
Gaglani M, Vasudevan A, Raiyani C, Murthy K, Chen W, Reis M, Belongia EA, McLean HQ, Jackson ML, Jackson LA, Zimmerman RK, Nowalk MP, Monto AS, Martin ET, Chung JR, Spencer S, Fry AM, Flannery B. (2020). Effectiveness of Trivalent and Quadrivalent Inactivated Vaccines against Influenza B in the United States, 2011-2012 to 2016-2017. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America