Figure 6.

Detection of vaccinia virus IgG antibodies in serum samples of 130 individuals born before and after the completion of smallpox vaccination in Brazil. Detection was performed by ELISA using purified inactivated VACV-Wyeth clone A111 as antigen. Results for each serum are represented by individual dots and expressed as arbitrary units. (A) Distribution of anti-VACV IgG values according to the year of birth. Black arrow points to 1979, when smallpox vaccination was ended in Brazil. (B) Serological response to VACV-Wyeth was plotted according to the presumed vaccination status. Individuals born before 1979 were considered vaccinated and individuals born after 1979 were considered unvaccinated. The blue circle refers to a laboratory worker recently and repeatedly vaccinated with the smallpox vaccine. The green circle corresponds to a pool of two convalescent sera from laboratory workers accidently infected with VACV. Dotted lines indicate the upper and lower limits of the test cut-off. **** p < 0.0001 (Mann–Whitney).