1907. Effect of Prior Season Vaccination on Serologic Response to Live Attenuated and Inactivated Influenza Vaccine in Children During 2014-2015
Session: Poster Abstract Session: Vaccines: Influenza
Saturday, October 10, 2015
Room: Poster Hall
Background: Influenza vaccination is recommended annually for children aged ≥6 months. Limited data are available about immune response to repeated vaccination over multiple seasons. Serologic response is dependent on age, preexisting antibody levels, and vaccine type; inactivated influenza vaccine (IIV) yields higher antibody levels than live attenuated influenza vaccine (LAIV). We assessed serologic response to vaccination among children during two consecutive influenza seasons with the same vaccine strain composition.

Methods: In fall 2014, we re-enrolled U.S. children aged 5–17 years from an observational study of serologic response to LAIV or IIV in 2013–14 (year 1). For 2014-15 (year 2), children aged ≤8 years without a contraindication received LAIV. Children aged 9–17 years were randomized to either LAIV or IIV. Pre- and postvaccination samples were tested by hemagglutination-inhibition (HI) for reactivity to H3N2 and pH1N1 vaccine strains. Endpoints were seroconversion (defined as 4 fold titer rise) and change in geometric mean titer (GMT) after vaccination. Χ2and paired t-test were used.

Results: Eighty-nine of 96 children had pre- and postvaccination titers in both seasons. Rise in GMT from year 1 pre- to year 2 postvaccination for both H3N2 and H1N1 was statistically significant for all groups except H1N1 in LAIV→LAIV recipients (p=0.12). The year 2 pre- and postvaccination GMT did not increase significantly among LAIV recipients, regardless of prior year vaccine type.

Year 1

Year 2

n

Mean age,

years

GMT H1N1

GMT H3N2

Year 1 pre-vaccination

Year 2 post-vaccination

Year 1 pre-vaccination

Year 2 post-vaccination

LAIV

LAIV

29

9.2

37

57

55

93

IIV

LAIV

31

12.1

42

116

42

117

IIV

IIV

16

12.9

58

287

31

236

LAIV

IIV

13

10.6

32

517

48

356

For H1N1, 77% of children receiving LAIV→IIV seroconverted in year 2 vs 25% of those receiving IIV→IIV (p=0.005). One child receiving LAIV in year 2 seroconverted to H1N1.  For H3N2, 46% of LAIV→IIV recipients seroconverted vs 19% in IIV→IIV recipients (p=0.2).

Conclusion: Vaccination over two seasons with no change in vaccine viruses resulted in increased H1N1 and H3N2 antibody titers; LAIV followed by IIV resulted in the greatest increase. Better understanding of the effects of prior LAIV on immune response to IIV is needed.

Pamela Talley, MPH, MD1,2, Jennifer King, MPH3, Huong Mclean, MPH, PhD3, Brendan Flannery, PhD4, Sarah Spencer, PhD5 and Edward Belongia, MD3, (1)Epidemiology Workforce Branch, Centers for Disease Control and Prevention, Atlanta, GA, (2)Infectious Disease Epidemiology, Prevention and Control, Minnesota Department of Health, St Paul, MN, (3)Center for Clinical Epidemiology and Population Health, Marshfield Clinic Research Foundation, Marshfield, WI, (4)Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, (5)Centers for Disease Control and Prevention, Atlanta, GA

Disclosures:

P. Talley, None

J. King, None

H. Mclean, MedImmune: Investigator , Research support

B. Flannery, None

S. Spencer, None

E. Belongia, Medimmune: Investigator , Research support

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