Scientists at the University of California, Riverside (United States) have unveiled a novel RNA-based vaccine strategy that is effective against any strain of a virus and safe for even infants and the immunocompromised. The vaccine, how it works, and a demonstration of its effectiveness in mice are described in a paper published today in the journal Proceedings of the National Academy of Sciences, according to a press release from UC Riverside. Read Also: Scientists reveal: Effectiveness of mpox vaccine decreases in a short time (Portuguese version) "What I want to emphasize about this vaccine strategy is that it is broad—applicable to any number of viruses—effective against any variant of a virus, and safe for a wide range of people. This could be the universal vaccine we have been looking for," said Rong Hai, a virologist at UC Riverside and the corresponding author of the paper, in a statement. Each year, researchers try to predict the four strains of influenza virus most likely to be prevalent during the upcoming flu season, and an updated vaccine must be taken annually. The same has been true for vaccines against SARS-CoV-2, the coronavirus that causes COVID-19, which have been reformulated to target subvariants of the dominant circulating strains. By targeting a part of the viral genome that is common to all strains of a virus, the new strategy would eliminate the need to create different vaccines. "Traditionally, vaccines contain a live, killed, or modified version of a virus. The body's immune system recognizes a protein on the virus and mounts an immune response," producing "T cells that attack the virus and stop it from spreading" and "memory B cells that train the immune system" to prevent future attacks. The newly unveiled vaccine "uses a modified live virus," but "it does not rely" on that immune response—which is why it can be given to infants with immature immune systems or to the immunocompromised—but instead on small RNA molecules that silence disease-causing genes. Read Also: Dengue. Is the risk serious here? From symptoms to care, doctor clarifies (Portuguese version) "A host—a person, a mouse, whoever is infected—will produce small interfering RNAs as an immune response to viral infection. Those siRNAs then knock down the virus," explained Shouwei Ding, a professor of microbiology at UC Riverside and the paper's lead author, in a statement. Since viruses cause disease because they produce proteins that block the host's siRNA response, creating a mutant virus that cannot produce the protein to suppress siRNA weakens the virus. "It can replicate to some extent, but then it loses the battle to the host's siRNA response," Ding said, adding: "A virus weakened in this way can be used as a vaccine to boost our siRNA immune system." The new strategy was tested in mutant mice, which lack T and B cells, and it was found that a single injection of the vaccine protected the mice from a lethal dose of the unmodified virus for at least 90 days. (Some studies show that nine days in mice is roughly equivalent to one human year.) Even newborn mice produce small RNA molecules, so the vaccine protected them as well. UC Riverside has filed a U.S. patent for this RNAi vaccine technology, and the researchers' next step is to create an influenza vaccine to protect children. Read Also: You should always close the toilet lid before flushing. Did you know that? (Portuguese version) "If successful, they will no longer have to rely on antibodies from their mothers," Ding said. The scientists also say that it is unlikely that a virus could mutate to evade this vaccination strategy. "Viruses can mutate in areas not targeted by traditional vaccines. However, in this case, the target of the thousands of small RNAs is their entire genome. They cannot escape," Hai said. By using a "cut and paste" approach with the strategy, the researchers also believe they could make a single vaccine for any type of virus. "There are several well-known human pathogens, such as dengue virus and SARS. They all have similar viral functions," so the new strategy "should be suitable for those viruses," Ding said. Read Also: Researchers are developing a vaccine against lung cancer (Portuguese version)