Explainer: Reaching swarm immunity with a viral pandemic

Sydney (Reuters)-We hope that the new coronavirus pandemic will bring “herd immunity” to the public consciousness and help this phenomenon delay or end its outbreak.

Flock immunity means that most of the community develops some degree of immunity to the virus, thereby reducing human-to-human transmission. As a result, the entire community is protected, not just those with immunity.

Graphic: How vaccines slow the spread of the virus here

Natural infection and vaccination

There are two routes to herd immunity: natural infection or vaccination.

Spontaneous infection means that many people have become ill and have recovered. However, with the new coronavirus, the degree of protection from natural infections is unknown. In addition, more people die while waiting for the herd to immunize than if the vaccine was produced.

“Risks are unacceptable,” said Catherine Bennett, epidemiology chairman of the Department of Health at Deakin University in Melbourne. “If you know little about the long-term effects, you can’t afford to infect people to reach the immunity of the herd.”

Vaccination can provide a wider range of immunity faster and more reliably.

There is no vaccine against COVID-19-a disease caused by a novel coronavirus-but trials at various stages are underway worldwide. It usually takes several years for a vaccine to be identified, tested, manufactured, and distributed for public use. Vaccine manufacturers want to dramatically compress the COVID-19 timeline with faster testing and larger production before the product succeeds.

Experts believe that if no other measures are taken, herd immunity can develop when 50-70% of the population is immunized by vaccination. The exact level depends on the effectiveness of the vaccine, but experts say it is up to 70%.

Vaccine distribution balance

How the vaccine is distributed affects its effectiveness. Uneven sharing, such as when the rich are more accessible than those in the poor, creates a secure cluster, but leaves a large area of ​​vulnerable people.

In the early stages of distribution, health care workers and other people at the forefront, or those who are considered to be the most vulnerable-the process known as targeted vaccination may be given higher priority. .. This is the risk of missing people who may be considered “superspreaders”, such as public transport workers.

Joel Miller, a senior lecturer in applied mathematics at La Trobe University in Melbourne, uses mathematical models to formulate policies and infectious diseases by governments and nonprofits.

Restriction of movement

The movement of people also affects the spread of the virus.

At low vaccination levels, the number of people who will eventually get infected is the same for a group of people who travel in a wide variety of people and a group of people who are relatively static. However, the static population is much slower to spread, and governments around the world are imposing lockdown measures.

Even if a high proportion of the population is vaccinated, the number of infections can be further reduced if people refrain from traveling.

While waiting

The new coronavirus spreads primarily through the droplets released when a person coughs, sneezes, or speaks.

Until the vaccine is developed, wearing a mask, keeping physical distance, and hand hygiene can reduce infection and boost the immunity of the herd.

Epidemiologists primarily agree that the combined approach is important given that early vaccines on the market are unlikely to be 100% effective.

“It’s about adding layers,” said Bennett of Deakin University. “It gives us more protection from the spread of the community. The situation is much better where the combination of measures is used.”