Herd immunity, or community immunity, is when a large part of the population of an area is immune to a specific disease. If enough people are resistant to the cause of a disease, such as a virus or bacteria, it has nowhere to go. Herd immunity protects at-risk populations. These include babies and those whose immune systems are weak and can’t get resistance on their own.
While not every single individual may be immune, the group as a whole has protection. This is because there are fewer high-risk people overall. The infection rates drop, and the disease peters (decrease or fade gradually before coming to an end) out.
With the rising number of cases of COVID-19 around the world, health officials continue to work to find the best way to protect the public from the disease. You may have heard health officials mention herd immunity as a possible way to contain the spread of COVID-19. Here’s what you need to know about herd immunity and how it may help slow the spread of the new Coronavirus.
World Health Organisation (WHO) said that herd immunity against COVID-19 should be achieved by protecting people through vaccination, not by exposing them to the pathogen that causes the disease. 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. Vaccinated people are protected from getting the disease in question and passing on the pathogen, breaking any chains of transmission.
How Is Herd Immunity Achieved?
There are two ways this can happen:
- You can develop resistance naturally. When your body is exposed to a virus or bacteria, it makes antibodies to fight off the infection. When you recover, your body keeps these antibodies. Your body will defend against another infection. This is what stopped the Zika virus outbreak in Brazil. Two years after the outbreak began, 63% of the population had had exposure to the virus. Researchers think the community reached the right level for herd immunity. 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.
- Vaccines can also build resistance. They make your body think a virus or bacteria has infected it. You don’t get sick, but your immune system still makes protective antibodies. The next time your body meets that bacteria or virus, it’s ready to fight it off. This is what stopped polio in the United States.
When does a community reach herd immunity? It depends on the reproduction number, or R0. The R0 tells you the average number of people that a single person with the virus can infect if those people aren’t already immune. The higher the R0, the more people need to be resistant to reach herd immunity.
Researchers think that the R0 for COVID-19 is between 2 and 3. This means that one person can infect two to three other people. It also means 50% to 67% of the population would need to be resistant before herd immunity kicks in and the infection rates start to go down.
New variants of the virus, for example, could create a new wave of infections, even in people who have been vaccinated or previously exposed. That could slow progress toward herd immunity – or, if the virus successfully evades vaccines, it could put herd immunity out of reach.
So far, the known variants are at least partially susceptible to vaccines, and it's not clear whether people who had previous infection can be reinfected with a new variant. In any event, the virus will continue to evolve.
Vaccine availability in Zimbabwe
On 2 February 2021, the Chinese ambassador to Zimbabwe said Zimbabwe will have access to a Chinese Covid-19 vaccine soon, as Beijing ramps up its availability to developing nations. End of January 2021, Zimbabwe health officials said Russia and China had approached it about supplying coronavirus vaccines. Covid-19 infections have escalated in Zimbabwe in 2021, with about 60% of its 33,548 cases and more than two-thirds of its 1,234 deaths recorded since New Year's Day as at 2 February 2021.
“Zimbabwe will be one of the first 14 countries to receive vaccine aid from China very soon,” Guo Shaochun, the Chinese ambassador to Zimbabwe, wrote on Twitter.
On 4 February 2021, the government clarified an earlier misunderstanding on how the vaccine will be rolled out in the country. The Minister of Finance and Economic Development Mthuli Ncube said that the vaccine will be available to citizens of Zimbabwe for free quashing the misunderstanding that those who require vaccination will need to pay for it.
Five Facts about Herd Immunity
- Heard immunity to a contagion requires a big majority of a region's people to become immune to it.
- Vaccines are crucial to achieving herd immunity
- Intermittent relaxing and tightening of social-distancing rules is likely for many months
- On-again, off-again social distancing orders may continue beyond next year
- Immunity for Covid-19 survivors seems likely, but not certain.
- , World Health Organisation, Published: 31 December, 2020, Accessed: 4 February, 2021
- Richard Harris, , NPR Science, Published: 3 February, 2021, Accessed: 4 February, 2021
- , Times Live, Published: 2 February, 2021, Accessed: 4 February, 2021
- , New Zimbabwe, Published: 4 February, 2021, Accessed: 4 February, 2021