Your Top Questions Answered
Question: Is it possible that one or more vaccines will be approved before the end of the year?
It is possible, but making sure that any vaccine is safe and effective takes time. Ordinarily new vaccines require a decade or more to develop. Scientists have been working on a COVID-19 vaccine for less than a year
, and there are over 50 COVID-19 vaccines currently undergoing clinical trials around the world. The usual process of vaccine development is long and difficult, intentionally so. Many vaccines never make it to the finish line. An approach turns out to be less promising than originally hoped, and is abandoned. A drug candidate may not produce the desired effect in trials or may be associated with unacceptable adverse effects. A lot of things can dramatically slow or stop a candidate vaccine. With COVID-19, the development timeline has been incredibly accelerated, in large part because so many people and resources are focused on the task, including at UC San Diego.
Question: Are all people infected by COVID-19 equally contagious?
There is a peak period of contagiousness just before and at the onset of symptoms, and then contagiousness decreases. By the time many people are sick enough to go to the hospital, they are substantially less contagious than just before or at the time of symptom onset. It is clear that some individuals are more contagious than others
. This can be due to higher viral load at the onset of symptoms, higher emissions of respiratory particles, or both. COVID-19 transmission does not require coughing or sneezing. Viral shedding can occur with talking – or merely breathing. It is known that some people exhale 10 times more aerosols when speaking than others
, although the reason is not understood. Some infected people don’t exhale much virus, while others exhale a lot for a few days, which can cause a superspreading event.
Question: How has physical distancing helped dramatically lower COVID-19 transmission rate?
Answer: Physical distancing is hugely important in reducing transmission. Mathematical analyses have indicated that in San Diego County, the effect of the initial stay-at-home orders and physical distancing that occurred in March reduced the effective reproduction number, which is the number of infections that an infected individual causes. Before physical distancing interventions, on average, each infected individual infected four to five other individuals; after physical distancing began, each infected individual only infected between 0.8 and one other individual. This is important because if the number is below one, it means that the epidemic is dying out and fewer infections are occurring with each transmission cycle. The message: continue to physically distance, mask and follow safety guidelines as we tackle this pandemic.