The conversation
How many people should get a COVID-19 vaccine to stop the coronavirus?
It has been clear for some time that, at least in the US, the only way out of the coronavirus pandemic will be through vaccination. The rapid introduction of coronavirus vaccines is underway, but how many people need to be vaccinated to control this pandemic? I am a computational biologist who uses data and computer models to answer biological questions at the University of Connecticut. I watched my COVID-19 epidemic with a computer model to predict the number of hospitalizations at John Dempsey Hospital of the University of Connecticut. This type of computer model and the underlying theory can also be used to calculate the vaccination rates needed to break the chain of transmission of the coronavirus. My estimate is that about 70% of the entire U.S. population needs to be vaccinated to stop the pandemic. But the difference in the way people behave in different parts of the country, as well as open-ended questions about whether the vaccine infection occurs completely or people just get sick, adds some uncertainty. Removal of transmission Clinical trials have shown that once someone is vaccinated against the coronavirus, they will not become ill with COVID-19. Someone who does not get sick can still be infected with the coronavirus. But let’s also assume that a vaccinated person cannot spread the virus to others, even though researchers still do not know if it is true. If enough of the population is vaccinated, the virus finds it difficult to find new people to infect and the epidemic begins to die out. And not everyone needs to be vaccinated, just enough people to stop the virus from spreading out of control. The number of people to be vaccinated is known as the critical level of vaccination. Once a population reaches that number, you get herd immunity. Herd immunity is when there are so many vaccines that an infected person can barely find someone who can become infected, and therefore the virus cannot spread to other people. It is very important to protect people who cannot be vaccinated. The critical level of vaccination depends on how contagious the disease is and how effective the vaccine is. Infection is measured by the basic reproduction number – R0 – how many people an infected person would spread the virus on average if there were no protective measures. The more contagious a disease is, the greater the number of people who need to be vaccinated to achieve a heard immunity. The higher the vaccine is effective, the fewer people need to be vaccinated. R0 values do not differ from place to place because their population behaves differently – social interactions are not the same in rural and urban places, nor in hot climates compared to cold. Using the data on positive cases, hospitalizations and deaths, my model estimates that Connecticut currently has a R0 of 2.88, which means that each infected person would transmit the virus to 2.88 other people on average if no mitigation measures were in place. . Estimates at the provincial level range from 1.44 in Alpine, California to 4.31 in Hudson, New Jersey, but finding a R0 value for the entire U.S. is especially difficult due to the diverse climate and because of the virus affected different areas in different areas. times – behavior was far from uniform. Estimates range from 2.47 to 8.2, although most researchers place R0 for the entire US at about 3. While R0 varies by location and between estimates, the efficacy of the vaccines is constant and well known. The Pfizer-BioNTech and Moderna vaccines are 95% and 94.5% effective, respectively, in preventing COVID-19. Using vaccine efficacy values and the R0, we can calculate the critical vaccination level. For Connecticut, with a R0 of 2.88, 69% of the population needs to be vaccinated. For the whole US, with R0 of 3, it would be 70%. In New York City it will be 80% with an estimated R0 of 4.26. Lots of uncertainty While the math is relatively simple, things get complicated when you consider important questions that epidemiologists do not yet have answers to. First, the critical vaccination level formula assumes that humans interact at random. But in the real world, people are in very structured networks, depending on work, travel, and social connections. When considering these contact patterns, some researchers found that the critical vaccination levels were significantly smaller compared to assuming random interactions. Unfortunately, other unknowns can have the opposite effect. Vaccination trials clearly show that vaccinated people do not get sick with COVID-19. But it is still unknown whether the vaccines prevent people from getting mild infections that they can pass on to others. If vaccinated people can still be infected and transmit the virus, the vaccination does not provide herd immunity – although it will still prevent serious illnesses and drastically reduce deaths. A final question that still needs to be answered is how long immunity to the coronavirus lasts after a person is vaccinated. If the immunity decreases after a few months, each individual will have to be vaccinated repeatedly. It is difficult to say with certainty how many people need to be vaccinated to end this pandemic. But still, the advent of COVID-19 vaccines was the best news in 2020. By 2021, as a large proportion of individuals in the U.S. get the vaccine, the country will be at the critical level of vaccination – whatever that may be. may be – so that life can begin to return to normal.[You need to understand the coronavirus pandemic, and we can help. Read The Conversation’s newsletter.]This article was published from The Conversation, a non-profit news site dedicated to sharing ideas from academic experts. It was written by: Pedro Mendes, University of Connecticut. Read more: * Test positivity: How this one figure declares that the US is not doing enough tests yet * What is not said why African Americans should not take the COVID- 19 vaccine Pedro Mendes is currently receiving funding from the National Institutes of Health. In the past, he has received research funding from the National Science Foundation, the British Biotechnology and Biological Sciences Research Council, the British Engineering and Physical Sciences Research Council, and the European Union.