LIVE POLIO IRUS VACCINES

162
Safety-Field Evidence of Safety
stool specimens were collected after Type 2 had
been fed to group B and before it was fed to
group A. The third, fourth, and fifth stool specimens
were collected after Type 1 had been fed
to group B, and before it was fed to group A.
The fourth, fifth, and sixth specimens were collected
after Type 3 had been fed to group B, and
before it was fed to group A. The community
spread of each type of poliovirus was thus measured
for a period of about eight weeks.
The collection of stool specimens was scheluled
for about 14 days after the feeding of virus. The
time elapsed between feeding and the collection
of the stool specimens was calculated from the
Wednesday of the week of feeding. The median
day of receipt of the second stool specimens was
14 days, the third stool specimen 13 days, and
the fourth stool specimen, 14 days after each immediately
preceding virus feeding. More than
93 per cent of these three stool specimens were
received within three days prior to, and six days
following, the median day of receipt for each
specimen. It will be noted in Table 1 that there
was some overlap between the, days for stool
collection and the subsequent feeding days; however,
no family was fed the vaccine (or placebo)
until the expected stool specimens were submitted.
The stool specimens were, in effect, the
"ticket" for the receipt of the vaccine or placebo
capsules. A total of only 15 stool specimens were
missing; 10 of 1728 were missing from the 288
adults, four of 1224 were missing from the 204
children, and one of 318 were missing from the
53 infants. Only one specimen (from an infant)
was unsatisfactory for virus isolation due to bacterial
contamination which was not controlled by
antibiotics.
Specimens were stored frozen (-20 ° C.) prior
to processing. For isolation, 20 per cent emulsions
of stool specimens were prepared in distilled
water by shaking for five minutes, centrifugation
at 1500 rpm. (I.E.C. No. 2) and 30
minutes at 13,000 rpm. (Servall). A portion of
the supernatant was diluted 1-2 with double
strength Hanks' balanced salt solution containing
600 units of penicillin and 600 micrograms of
streptomycin per ml. Supernates of processed
stool specimens were stored frozen and were
thawed prior to inoculation when 0.1 ml. of each
processed stool specimen was inoculated into each
of two HeLa cell TC tubes. The procedure for
preparation of the HeLa cell TC tubes has previously
been published.' Inoculated TC tubes
were examined after one, three, five, and seven
days of incubation at 37 ° C. When characteristic
cytopathogenicity was observed after at least
TABLE 1. CHRONOLOGY OF SPECIMEN COLLECTION AND VACCINE FEEDING
MINNESOTA STUDY WITH ORAL POLIOMYELITIS VACCINE-1958
DATES
GROUP A
STOOL
BLEEDINGS SPECIMENS FEEDINGS
GRoUP B
STOOL
BLEEDINGS SPECIMENS FEEDINGS
1-27, 2-1
1-28, 2-6
2-3, 2-8
2-16, 2-24
2-24, 3-1
3-9, 3-19
3-17, 3-22
3-30, 4-8
3-31, 4-5
4-7, 4-12
4-20, 4-28
4-25, 5-1
5-11, 5-20
5-15, 5-21
6-2, 6-7
1st
2nd
3rd
lst
2nd
3rd
4th
5th
6th
Placebo
Placebo
Placebo
Type 2
Type 1
Type 3
* The time prior to the feeding of Type 2 vaccine to group A is the control period.
1st
2nd
3rd
1st
2nd
3rd
4th
5th
6th
Type 2
Type 1
Type 3
Placebo
Placebo
Placebo
Placebo