Safety and infectivity of two doses of live-attenuated recombinant cold-passaged human parainfluenza type 3 virus vaccine rHPIV3cp45 in HPIV3-seronegative young children

Englund, J. A.; Karron, R. A.; Cunningham, C. K.; Larussa, P.; Melvin, A.; Yogev, R.; Handelsman, E.; Siberry, G. K.; Thumar, B.; Schappell, E.; Bull, C. V.; Chu, H. Y.; Schaap-Nutt, A.; Buchholz, U.; Collins, P. L.; Schmidt, A. C.

Vaccine. 2013 Oct 10; 31(48):5706-12


BACKGROUND: Human parainfluenza virus type 3 (HPIV3) is a common cause of upper and lower respiratory tract illness in infants and young children. Live-attenuated cold-adapted HPIV3 vaccines have been evaluated in infants but a suitable interval for administration of a second dose of vaccine has not been defined. METHODS: HPIV3-seronegative children between the ages of 6 and 36 months were randomized 2:1 in a blinded study to receive two doses of 10(5) TCID50 (50% tissue culture infectious dose) of live-attenuated, recombinant cold-passaged human PIV3 vaccine (rHPIV3cp45) or placebo 6 months apart. Serum antibody levels were assessed prior to and approximately 4-6 weeks after each dose. Vaccine virus infectivity, defined as detection of vaccine-HPIV3 in nasal wash and/or a>/=4-fold rise in serum antibody titer, and reactogenicity were assessed on days 3, 7, and 14 following immunization. RESULTS: Forty HPIV3-seronegative children (median age 13 months; range 6-35 months) were enrolled; 27 (68%) received vaccine and 13 (32%) received placebo. Infectivity was detected in 25 (96%) of 26 evaluable vaccinees following doses 1 and 9 of 26 subject (35%) following dose 2. Among those who shed virus, the median duration of viral shedding was 12 days (range 6-15 days) after dose 1 and 6 days (range 3-8 days) after dose 2, with a mean peak log10 viral titer of 3.4PFU/mL (SD: 1.0) after dose 1 compared to 1.5PFU/mL (SD: 0.92) after dose 2. Overall, reactogenicity was mild, with no difference in rates of fever and upper respiratory infection symptoms between vaccine and placebo groups. CONCLUSION: rHPIV3cp45 was immunogenic and well-tolerated in seronegative young children. A second dose administered 6 months after the initial dose was restricted in those previously infected with vaccine virus; however, the second dose boosted antibody responses and induced antibody responses in two previously uninfected children.

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