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3. That only the live virus vaccine would produce

the so-called "herd effect" thus further protecting unvac

cinated members of the population by decreasing the spread

of wild viruses. It was claimed that this could not be

accomplished with the killed virus vaccine.

4.

That the live virus vaccine produced longer

lasting immunity than did the killed virus vaccine.

It is now 1976, and data are available from more than 21 years of experience with the killed virus vaccine and more than 14 years with the live. We can now re-examine the 1961 hypotheses upon which were based the proposed switch from the use of a killed to a live poliovirus vaccine in the U.S. The data now indicate that:

1. Contrary to beliefs in 1961, the live oral polio
vaccine has been shown to be not completely safe, since
there is a small but definite inherent risk of its causing
polio in recipients of the vaccine and their contacts. More
than 140 such cases have thus far accumulated in the United

States, and in the last several years, the live vaccine has
been the principal if not the sole cause of domestically
arising cases of polio. In other words, it may be said that,

79-371 O-77-2

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at the present time, the risk of acquiring polio from

the live virus vaccine is greater than from naturally

occurring viruses.

2. Contrary to beliefs held in 1961, the

"spread of immunity" by infection of contacts is not always harmless and contributes to the public risk associated with the use of the live virus vaccine.

It is now clear that if the killed virus vaccine had not

already been administered there would have been many more cases of poliomyelitis resulting from use

of the live virus vaccine.

3. Contrary to beliefs held in 1961, it has been shown that the killed poliovirus vaccine is effective in eradicating the disease, and in eliminating wild poliovirus from the community. It has also been shown that the so-called "intestinal immunity", or "natural immunity", produced by the live virus vaccine is not important for a herd effect, and that, in fact, the killed vaccine does produce a herd effect and widespread community protection. This has been demonstrated in

countries where only killed virus has been used as you

will hear from Dr. Penttinen.

vaccine are not required any more than are booster doses

of the live virus vaccine.

The following arguments in support of the routine use in the U.S. of a live poliovirus vaccine have been made:

1. That a vaccine given orally is more acceptable

to the public than a vaccine given by injection. However, by 1961 a higher proportion of children had received three doses of killed virus vaccine by injection than has even now been achieved with the oral vaccine. Furthermore, more children have received three injections of diptheria, tetanus and pertussis vaccine than have received three feedings of the oral polio vaccine. Moreover, killed polio vaccine can be admixed with the vaccine for diptheria, tetanus and pertussis, in any combination, as is done in some countries. Thus the ideal

of a single vaccine for this group of childhood diseases,

including polio, is a practical reality in certain other countries.

The advantage for polio immunization is that DTP vaccine is

already in routine use for all children.

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2. That the cost per dose of the oral vaccine is

less. I am not a merchandising expert but it seems

evident that when looking at cost one has to consider

volume of demand, additional cost of shipping and storage
in the frozen state, the final cost to the patient in terms
of number and cost of office visits as well as insurance

and liability burdens which are also passed on to the
consumer. These also apply to government-operated clinics,

which is the public consumer.

3. That if a choice of the live or killed poliovirus vaccine were offered, the public would be inclined toward the safer killed vaccine, and this would subject the country to virus invasion through immigrants or travelers especially across the Mexican border. However, as I have already noted, the killed vaccine induces the herd effect and does provide

community protection. I published such evidence prior to

the time of the initial policy decision to favor the live

vaccine. I repeat it now. And I call attention to the accumu

lated evidence in the scientific literature.

I concur that the live virus vaccine would be more suitable than

the killed vaccine for use in suppressing an outbreak should any arise

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in communities with low vaccination rates. However, I regard a killed poliovirus vaccine as more suitable for routine immunization because of differences in risk.

The ultimate goal in the control of any infectious disease is the prevention of outbreaks. This can be accomplished by sufficiently widespread use of the safest as well as the most effective vaccines that we are able to create.

Surely, by taking advantage of our knowledge of the anatomy of viruses and of the structure and function of their genetic and somatic constituents, we should be able to improve upon our present methods of immunization toward eliminating risk rather than having to improve upon methods of compensation for vaccine damage.

For your further information and for clarification, I have included some of the data upon which the points I have made are based.