Table 2.

Overview of the statistical analyses

Experiments	${\widehat{R}}_{low}$	${\widehat{R}}_{high}$
1 + 5	3.4 (1.5–8.4)	1.1 (0.46–1.7)
2 + 6	0.95 (0.27–2.8)	0.19 (0.023–0.79)
3 + 7	>1.8a	0.38 (0.044–0.98)
4 + 8	>2.1a	1.5 (0.50–3.9)
All	3.1 (1.8–4.3)	0.72 (0.41–1.0)

Data are the combined results of Experiments 1 and 5 (vaccine, La Sota; virus, NL93), Experiments 2 and 6 (vaccine, La Sota; virus, Herts33/56), Experiments 3 and 7 (vaccine, La Sota; virus, California71), Experiments 4 and 8 (vaccine, Ulster; virus, NL93), and all experiments taken together. ${\widehat{R}}_{low}$ and ${\widehat{R}}_{high}$ represent the maximum likelihood estimates of R_low and R_high, which are calculated using the infection data of Table 1. The 95% confidence intervals are presented in parentheses.

^aOnly the lower bound of the (one-sided) 95% confidence interval is given.