The immunizing potency of alcohol-killed and alcohol-preserved typhoid vaccine after storage for ten Years

Abstract

1. Alcohol-killed and alcohol-preserved typhoid vaccine retains its power of stimulating Vi- and O-antibody formation unimpaired during storage at 1–2° C. for at least 10 years.2. The Vi antibody induced by immunization with the 10-year-old vaccine possesses full ‘functional efficacy’ in passive-immunity tests in mice.3. The expiry date of this type of vaccine can be extended to a period of 10 years, provided the vaccine is kept in cold storage.4. Alcoholized vaccine can serve as ‘standard vaccine’ in any future attempt at standardization of the potency of typhoid vaccine.

Chrome typhoid vaccine

“…It will be noted that improper storage of the experimental chrome vaccine at 410 C affected the Vi-antigen markedly, as shown by all the in vivo tests; but this was a severe and artificial stability test, which does not contradict the other good qualities of the chrome vaccine-namely its Vi-antigen stability and its protective properties in both active and passive mouse protection tests. The conclusions to be drawn from this series of tests, however, have to be considered against the results of the field trials in Yugoslavia and the laboratory 48 E. E. VELLA Chrome typhoid vaccine assays of the vaccines used in that trial (Cvjetanovic, 1957;Yugoslavia Typhoid Commission, 1957;Edsall, Carlson, Foomal & Benenson, 1959;Standfast, 1960), in which the phenolized vaccine gave better protection to vaccinated persons than the alcoholized vaccine, notwithstanding the generally recognized preserving effect of alcohol treatment on the Vi-antigen of typhoid suspensions on one hand and the damaging effect of heat and phenol on the other (Felix, Rainsford & Stokes, 1941;Bensted, 1940;Climie, 1942;Felix & Anderson, 1951). The Japanese workers have conducted human trials on numerous occasions with satisfactory results, and have demonstrated the rise of Vi-antibodies which was effected by the chrome vaccine, as compared with the usual lack of these antibodies when heat-killed vaccines are used.…”

Solubility of Vi Antigen ofSalmonella Typhi

“…Felix (1941) devised a vaccine giving rise to both 0 and Vi antibodies; the bacteria were harvested from agar cultures in 75 % alcohol, suspended in a solution of 25 % alcohol in saline and stored at 1-20 C. Rainsford (1942) showed that this vaccine rapidly lost Vi antigenicity, as measured by the ability to agglutinate with Vi antibodies, when stored at 250 C. He suggested the preservation of Vi antigen in a 32 % NaCl solution, or by drying from an acetone suspension. Ether has been used by Gohar & Elian (1942) for a similar purpose as has 34 % sucrose (Loureiro; see Felix & Anderson, 1951).…”