Live-Virus Vaccine

The U.S. Public Health Service this week summoned its Committee on Live Poliovirus Vaccine to meet on its Bethesda, Md. campus to study reports of the oral vaccines' safety, potency and effectiveness. The evidence for the panel, headed by PHS's Dr. Roderick Murray, was confusing and often contradictory. The consensus: while live-virus vaccines, taken by mouth (as distinct from the killed-virus, Salk-type vaccine, which must be injected), are indeed promising, there is little chance that any will be licensed for general U.S. use until next summer or later.

A major source of data is Florida's Dade County (Miami and environs), locale for the biggest U.S. field trial of any live-virus vaccine (TIME, Feb. 29). As of April 30, when Florida's polio season was beginning and authorities halted vaccinations to keep test results as clear as possible, no fewer than 413,336 residents had taken a swig of the sweetish, pink vaccine developed by Lederle Laboratories' Dr. Herald R. Cox.

Cause & Effect? The first and most vital question was: Is the vaccine safe? Last week Dade's Health Commissioner Turner E. Cato listed seven cases of paralytic polio in the county since vaccine feeding began--about average for the date. Two victims had not taken the vac cine, but five patients (including one severely paralyzed) became ill seven to 14 days after taking it. It may never be possible to tell whether the infection came from the vaccine. If a patient develops paralytic polio about ten days after vaccination, it is extremely difficult to tell where he got the infectious virus. The hope is that by detailed studies, virologists may find elusive chemical markers to show whether the disease was caused by Lederle virus strains or by wild strains.

At best, the studies will take months.

The fact that no new case of paralytic polio has developed in Dade County since May 3 is encouraging. In previous years, even since Salk, there have been as many as half a dozen. "On the surface," says a PHS epidemiologist, "the vaccine appears safe and efficient. But vaccines are supposed to prevent polio, and we won't know whether this one has done so until the end of the season."

Monkey Tricks. Other research under study at Bethesda raises the problem of ensuring the safety of any live-virus material grown in tissue cultures of monkeys' kidney cells. The kidneys of the monkey species used in vaccine manufacture are loaded with native viruses. The worst of these is Herpesvirus simiae, or "B virus," close kin to man's benign cold-sore virus. It apparently gives the monkey nothing worse than fever blisters; in man it is almost invariably fatal. In Salk vaccine these B virus particles were killed by formaldehyde, but in making an oral vaccine of live, attenuated viruses, no inactivating process is used.

To complicate the issue. Dr. Maurice R. Hilleman of Merck Sharp & Dohme (which, by no coincidence, has an improved killed vaccine ready for marketing) has discovered other monkey viruses in oral vaccines prepared by Cincinnati's Dr. Albert B. Sabin. The PHS's Division of Biologics Standards has independently confirmed Hilleman's findings. Whether these monkey viruses are dangerous for man is not yet known, but the PHS wants to take no chances. Nor is it known how often the domesticated polio strains used in live-virus vaccines revert to a feral state, which may be dangerous, though detailed studies are going on at several research centers.

Triple Negative. For safety's sake, the Live Poliovirus committee is wrestling with an eight-page schedule of precautions for would-be makers of oral vaccines.

Some of these, the manufacturers argue, are unrealistic, e.g., a suggestion that the vaccines must be tested first in 100,000 "triple-negative" subjects (those who have no antibodies against any of the three types of poliovirus, meaning that they can have had no Salk vaccine). Such people are hard to identify.

Whatever the detailed requirements, manufacturers will have to produce five successive batches of consistent safety and potency before the live-virus vaccine can be licensed. This is likely to take until the summer of 1961. Meanwhile, all authorities agree in urging the public not to defer Salk shots while waiting for the oral alternative. "We already know in a crude way that it's a generally safe vaccine," says a PHS technical expert. "It's the fine points that are still at issue."

This file is automatically generated by a robot program, so reader's discretion is required.