non-pathogenic viruses, as DNA, and others), are under development. Efforts have also been undertaken to develop universal vaccines that specifically activate a T-cell response, based on clinical data showing that people with a strong, early T-cell response have better outcomes when infected with influenza and because T-cells respond to conserved epitopes. The challenge for developers is that these epitopes are on internal protein domains that are only mildly immunogenic. Along with the rest of the vaccine field, people working on universal vaccines have experimented with vaccine adjuvants to improve the ability of their vaccines to create a sufficiently powerful and enduring immune response. Oral influenza vaccine As of 2019, an oral flu vaccine was in clinical research. The oral vaccine candidate is based on an adenovirus type5 vector modified to remove genes needed for replication, with an added gene that expresses a small double-stranded RNA hairpin molecule as an adjuvant. In 2020, a PhaseII human trial of the pill form of the vaccine showed that it was well tolerated and provided similar immunity to a licensed injectable vaccine. COVID-19 An influenza vaccine and a COVID-19 vaccine may be given safely at the same time. Preliminary research indicates that influenza vaccination does not prevent COVID-19, but may reduce the incidence and severity of COVID-19 infection. Criticism Tom Jefferson, who has led Cochrane Collaboration reviews of flu vaccines, has called clinical evidence concerning flu vaccines "rubbish" and has therefore declared them to be ineffective; he has called for placebo-controlled randomized clinical trials, which most in the field hold as unethical. His views on the efficacy of flu vaccines are rejected by medical institutions including the CDC and the National Institutes of Health, and by key figures in the field like Anthony Fauci. Michael Osterholm, who led the Center for Infectious Disease Research and Policy 2012 review on flu vaccines, recommended getting the vaccine but criticized its promotion, saying, "We have overpromoted and overhyped this vaccine... it does not protect as promoted. It's all a sales job: it's all public relations." Veterinary use Veterinary influenza vaccination aims to achieve the following four objectives: Protection from clinical disease Protection from infection with virulent virus Protection from virus excretion Serological differentiation of infected from vaccinated animals (so-called DIVA principle). Horses Horses with horse flu can run a fever, have a dry hacking cough, have a runny nose, and become depressed and reluctant to eat or