These challenges should preclude any plans that try to increase immunity within a population by allowing people to get infected.Īlthough older people and those with underlying conditions are most at risk of severe disease and death, they are not the only ones at risk.įinally, while most infected people get mild or moderate forms of COVID-19 and some experience no disease, many become seriously ill and must be admitted into hospital. Until we better understand COVID-19 immunity, it will not be possible to know how much of a population is immune and how long that immunity last for, let alone make future predictions. There have also been reports of people infected with COVID-19 for a second time. Most people who are infected with COVID-19 develop an immune response within the first few weeks, but we don’t know how strong or lasting that immune response is, or how it differs for different people. We are still learning about immunity to COVID-19. Seroprevalence surveys suggest that in most countries, less than 10% of the population have been infected with COVID-19. The vast majority of people in most countries remain susceptible to this virus. Letting COVID-19 spread through populations, of any age or health status will lead to unnecessary infections, suffering and death. For polio, the threshold is about 80%. The proportion of the population that must be vaccinated against COVID-19 to begin inducing herd immunity is not known. This is an important area of research and will likely vary according to the community, the vaccine, the populations prioritized for vaccination, and other factors.Īchieving herd immunity with safe and effective vaccines makes diseases rarer and saves lives.įind out more about the science behind herd immunity by watching or reading this interview with WHO’s Chief Scientist, Dr Soumya Swaminathan.Īttempts to reach ‘herd immunity’ through exposing people to a virus are scientifically problematic and unethical.
The remaining 5% will be protected by the fact that measles will not spread among those who are vaccinated. For example, herd immunity against measles requires about 95% of a population to be vaccinated. The percentage of people who need to be immune in order to achieve herd immunity varies with each disease. Read our Q&A on vaccines and immunization for more information.
due to health conditions like allergic reactions to the vaccine) safe and protected from the disease. To safely achieve herd immunity against COVID-19, a substantial proportion of a population would need to be vaccinated, lowering the overall amount of virus able to spread in the whole population. One of the aims with working towards herd immunity is to keep vulnerable groups who cannot get vaccinated (e.g.
Visit our webpage on COVID-19 and vaccines for more detail. Vaccinated people are protected from getting the disease in question and passing on the pathogen, breaking any chains of transmission. Vaccines train our immune systems to create proteins that fight disease, known as ‘antibodies’, just as would happen when we are exposed to a disease but – crucially – vaccines work without making us sick. Read the Director-General’s 12 October media briefing speech for more detail. Herd immunity against COVID-19 should be achieved by protecting people through vaccination, not by exposing them to the pathogen that causes the disease. WHO supports achieving 'herd immunity' through vaccination, not by allowing a disease to spread through any segment of the population, as this would result in unnecessary cases and deaths. 'Herd immunity', also known as 'population immunity', is the indirect protection from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous infection.
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