a1 Department of Bacteriology, University of Liverpool
a2 Ministry of Health
Following primary vaccination no antibody was detected up to the tenth day. After this time neutralizing antibody and antihaemagglutinin were present in the majority of individuals, while, with the technique used, complement-fixing antibody was found in less than half those examined. Neutralizing antibody may be found in the blood more that 20 years after primary vaccination; by this time very few show antihaemagglutinin and then only in low titre. Complement-fixing antibody was not found more than 6 months after primary vaccination.
In revaccinated individuals the antibody response tended to be higher than after primary vaccination and, when it occurred, often appeared within a week. This suggests that prompt revaccination of smallpox contacts may offer even greater protection than does primary vaccination.
The neutralization test is a better measure of immunological response than are either of the other two tests, for these may give a negative result even though there may be a well-marked rise in neutralizing antibody. The ‘early’ type of reaction to revaccination was associated with an antibody response in only about half the subjects examined. In the remainder, the skin reaction, although identical in appearance, must be regarded as allergic in nature and not accompanied by increase in immunity.
(Received April 17 1958)