Table 3.

Respiratory Syncytial Virus (RSV)-Specific Serum Antibody Responses Before and After Inoculation and RSV Season Surveillance

Group	No. of Children	Serum RSV-Neutralizing Antibodiesa						Serum IgG ELISA RSV F Antibodiesa
		Inoculation			Surveillance			Inoculation			Surveillance
		Preb	Postc	≥4-Fold Rise N (%)e	Pred	Postd	≥4-Fold Rise N (%)f	Preb	Postc	≥4-Fold Rise N (%)e	Pred	Postd	≥4-Fold Rise N (%)f
Vaccine	20	2.3 (2.3–2.3)	6.4 (5.7–7.1)	17 (85)	6.2 (5.6–7.1)	6.6g (5.6–8.8)	6g (32)	7.1(5.9–8.9)	14.0 (12.7–14.8)	17 (85)	13.8 (12.7–14.8)	13.7g (12.6–15.6)	5g (26)
Placebo	11	2.9 (2.3–2.3)	2.3 (2.3–2.3)	0 (0)	2.3g (2.3–2.3)	6.2g (5.6–7.9)	8g (80)	7.2 (5.9–8.8)	6.7 (4.6–8.9)	2 (18)	6.8g (5.2–8.9)	15.2g (14.8–15.6)	8g (80)

Abbreviations: ELISA, enzyme-linked immunosorbent assay; Ig, immunoglobulin.

^aSerum RSV 60% plaque reduction neutralizing titer (PRNT₆₀) was determined by complement-enhanced 60% plaque reduction neutralization assay; serum IgG titers to RSV F were determined by ELISA to baculovirus-expressed RSV F protein. Titer results are expressed as median reciprocal log₂, with the 25th and 75th percentiles indicated in parenthesis, determined for all participants in each group. Specimens with titers below the limit of detection were assigned reciprocal titers of 2.3 log₂ (PRNT₆₀) and 4.6 log₂ (ELISA).

^bBefore inoculation.

^cPostinoculation at study day 56.

^dPresurveillance, collected October 1–31 or on day 56 if on or after October 1; postsurveillance, collected April 1 to 30 at approximately 6 months postinoculation (1 vaccine recipient had the last visit in July).

^eNumber and percentage of vaccine and placebo recipients with ≥4-fold increase in antibody titers between preinoculation and postinoculation.

^f Number and percentage of vaccine and placebo recipients with ≥4-fold increase in antibody titers between presurveillance and postsurveillance.

^gOne participant had missing data at this time point.