Herd Immunity
Herd immunity is a form of indirect protection from infectious disease.
It can occur with some diseases when a sufficient percentage of a population has become immune to an infection, whether through vaccination or previous infections, thereby reducing the likelihood of infection for individuals who lack immunity.
Immune individuals are unlikely to contribute to disease transmission. As a result, the chain of infection gets disrupted, and stops or slows the spread of disease.
Greater the proportion of immune individuals in a community, the smaller the probability that non-immune individuals will come into contact with an infectious individual.
Individuals can become immune by recovering from an earlier infection or through vaccination.
Why it is important?
Often, a percentage of the population must be capable of getting a disease for it to spread. This is called a threshold proportion.
If the proportion of the population that is immune to the disease is greater than this threshold, the spread of the disease will decline. This is known as the herd immunity threshold.
The more contagious disease is, the greater the proportion of the population that needs to be immune to the disease to stop its spread.
How it is achieved?
There are two main ways to get herd immunity against COVID-19
1. Infection
2. Vaccination
Natural Infection
Herd immunity can be achieved when enough people in the population have recovered from a disease and have developed protective antibodies against future infection.
#Problems on relying on community infection includes –
- * Reinfection –
It is not clear how long you an protected from getting sick again after recovering from COVID-19. Even if you have antibodies, it’s possible that you could get COVID-19 again.
* Health impact –
A higher number of infections could lead to serious complications and millions of death, especially among older people and those who have existing health conditions. The health care system could quickly become shaken.
Vaccination - Herd immunity also can be reached when enough people have been vaccinated against a disease and have developed protective antibodies against future infection. Unlike the natural infection method, vaccines create immunity without causing illness or resulting complications.
- Using the concept of herd immunity, vaccines have successfully controlled contagious diseases such as smallpox, polio, Diptheria, rubella, etc.
- Herd immunity makes it possible to protect the population from disease, including those who can’t be vaccinated, such as newborns or those who have compromised immune systems.
Why it is difficult to reach Herd immunity through vaccination in COVID-19?- There are so many reasons that we have not yet achieved herd immunity target through vaccination in the case of COVID-19. Some of the reasons include-
• Vaccine hesitancy –
Some people may object to getting a COVID-19 vaccine because of religious objections, fears about possible risks, or skepticism about the benefits.
• Protection questions-
* It’s not clear how long the COVID-19 vaccine will protect you from COVID-19
* Further research is needed to see how much the COVID-19 vaccine reduces transmission of the COVID-19 virus.
* Research suggests that COVID-19 vaccines may have lower efficacy against some of the variants of the COVID-19 virus.
New variants, which could be more resistant to vaccines, are regularly emerging.
• Uneven vaccine distribution-
The distribution of COVID-19 vaccines has greatly varied among and within countries.
If one community achieves a high COVID-19 vaccination rate and surrounding areas don’t, outbreaks can occur whenever the population’s mix.
What are the challenges to develop Herd immunity against COVID-19?
The main obstacle in developing herd immunity against COVID-19 right now is that the virus that causes the disease is “novel” or new. It means that this virus hasn’t infected humans before and everyone is at risk of infection. There is no preexisting immunity available in the human body. - Another matter of concern barrier is that we don’t know how strong the immune protection is or how long it will last in people who have had COVID-19
While there are now vaccines to protect against COVID-19, still it may take months for people to get their complete vaccine protection. It is expected, that the vaccines will eventually help bring the spread under control. Researchers estimate that 75-80% of the population would need to be vaccinated before we can have herd immunity.
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- There are so many reasons that we have not yet achieved herd immunity target through vaccination in the case of COVID-19. Some of the reasons include-
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