Table 1.

Vaccination of members of the civilian conservation corps, 1934–1937

	Vaccinated	Non-vaccinated	Comments
1933–4	3,126 (0)	9,000 (8)	No pneumonia in vaccinated versus 8 cases among unvaccinated
1934–5	14,000 (13)	12,000 (23)	Vaccine appeared to be protective, but results difficult to interpret because of heterogeneity amongst the groups
1934–5	14,881 (18)	18,000 (39)	No type 1 or type 2 pneumonia in the vaccinated group versus 6 of each type among the controls
1936–7	10,740 (13)	14,494 (24)	Much better follow-up of subjects No pneumonia due to type 1 or 2 pneumococcus in the vaccinated group versus 13 cases in the controls

Vaccination with type 1 and type 2 capsular polysaccharides. Results are shown as numbers in each group with patients who developed pneumonia during the period of observation shown in parentheses

From reference [24]