Is the polio vaccine still used today?

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Some vaccines not only protect against the pathogens against which they were designed. After the introduction of the oral polio vaccine, it was discovered that the vaccinated children were also less likely to develop other infections. This applies once to related pathogens.

For example, a polio outbreak that occurred in Singapore in 1959 could be stopped with a monovalent vaccine against type 2 poliovirus, although the diseases were triggered by type 1 polioviruses. In 1975, mass polio vaccination in Bulgaria reduced the number of polio-like illnesses caused by enterovirus 71, a distant relative of the poliovirus. It has been proven that the polio vaccines do not produce cross-immunity.

Studies from the 1960s and 1970s found that polio vaccination reduced the incidence of influenza infections by a factor of 3.8. Genital herpes diseases also seem to heal faster after a polio vaccination. In Finland, after the polio vaccination, there was a decrease in acute otitis media caused by other viruses and bacteria.

Similar protective effects were observed after the MMR vaccination or after the BCG vaccination. What all the vaccinations mentioned have in common is that they are carried out with weakened live pathogens. Researchers attribute a broad protective effect to an activation of the unspecific immune defense, which also blocks other pathogens through the increased release of interferons.

With the BCG vaccination, emergency activation of the granulocytes should play a role, which could also protect against sepsis. In contrast to vaccination protection, which stimulates the formation of antibodies and memory cells in the long term, it seems to be a temporary phenomenon that disappears relatively quickly.

Could this protective effect be used to protect people during the current corona crisis and to bridge the time until a targeted vaccine? The idea is currently being tested in two clinical studies. In Australia, the BRACE study is currently randomizing over 10,000 hospital employees to vaccination with BCG or placebo. The same strategy is being investigated in the BCG-CORONA study on 1,500 hospital employees in the Netherlands. Results from the two studies are expected in October.

The US Food and Drug Administration (FDA) has now proposed the use of oral polio vaccination in Science. Konstantin Chumakov's team hopes for a particularly strong effect, since the poliovirus, like SARS-CoV-2, is one of the positive-strand RNA viruses.

The use of the oral polio vaccine offers several advantages over BCG, write the FDA staff: The polio vaccine has been shown to be safe for decades. Side effects are rare. Vaccine-associated paralytic polio (VAPP), which is triggered by reverse mutation of the vaccine into a pathogenic agent, only occurs in isolated cases (1 case in 3 million vaccinations).

They could also be safely avoided by a subsequent vaccination with the inactivated poliomyelitis vaccine. A BCG vaccination, on the other hand, is more often associated with side effects. About 1% of those vaccinated would need medical attention.

Oral polio vaccines are easy to manufacture and available in large quantities. About 1 billion doses would be used annually. With the BCG vaccine, however, there could be delivery bottlenecks.

The FDA staff first suggest that a randomized study be conducted. If this is successfully completed, the populations most at risk from COVID-19 could be protected. However, it would be best if the entire population were vaccinated.

It remains to be seen whether such vaccine studies will come about. The virologist Thomas Mertens from the Ulm University Hospital has expressed skepticism to the German news agency.

Global use is hardly conceivable, says the chairman of the Standing Vaccination Commission (STIKO) at the Robert Koch Institute, especially since the strategy of the World Health Organization is currently to convert the polio vaccination to a vaccination with inactivated viruses in order to eradicate the poliovirus type 1 - of the only remaining wild polio pathogen - to enable. Vaccinating the population with the oral vaccine could jeopardize this goal, as vaccine viruses would again circulate, from which a new wild type could develop again through reverse mutations.