When does a pandemic end?

Virus Outbreak Herd Immunity
Posted at 5:56 PM, Oct 01, 2021
and last updated 2021-10-01 19:19:49-04

Nueces county saw its first case of the COVID-19 strain on March 21, 2020.

A little more than a year and a half later, we're still living through the pandemic.

Vaccines to help control the novel coronavirus have been available in the Coastal Bend since January, and new case counts slowly began to trend downward as more people were immunized. However, the Delta variant brought a resurgence in July that is just now beginning to abate.

So when does a pandemic officially "end?" At what point does a virus become as commonplace as the flu, or as controlled as polio or smallpox?

The easy answer: When we reach herd immunity.

Herd immunity is made up of a combination of

  • people's bodies being able to resist the virus using the antibodies it leaves, and
  • immunity brought on by being vaccinated.
Vaccination clinic
20% of the population in the Coastal Bend is fully vaccinated

That's why medical and public health officials have encouraged people to get vaccinated since the beginning.

"The Delta variant, being highly transmissible, what it'll probably do is catch up to all the unvaccinated people within a year or so," said Corpus Christi-Nueces County Public Health District Local Health Authority Dr. Srikanth Ramachandruni. "But we don't want to achieve the herd immunity by means of natural infection -- which is the wrong way to do it -- when we have effective vaccinations in the community."

Vaccines are what ultimately curbed polio and smallpox, said Corpus Christi-Nueces County Public Health District Clinical Director Dr. Kim Onufrak.

However, comparing smallpox and polio to the COVID-19 strain of coronavirus is like comparing apples and oranges, Ramachandruni said. So is comparing it to the flu, for that matter.

"That's the confusion everybody has," he said. "Everybody's trying to compare the COVID with the flu virus. Both are different viruses, and both have different sizes."

Flu sick

The size and make-up of a virus matter, Ramachandruni said, because they affect how the virus behaves. Smaller viruses are considered less stable, and more prone to mutate. That's why, in certain years, flu vaccines are less effective.

In that case, the vaccine still helps, just not as much as it could have, because vaccines are designed to protect against one strain of the flu when it hits the market.

Ramachandruni said virologists don't believe COVID-19 variants will be as prevalent as flu variants

"Like flu -- the incubation period is two days, and the COVID variant incubation period is about five days," he said. "So if you give a vaccination to the COVID variants, it will work better compared to the flu vaccine and the flu variants because the incubation period is two days. By the time the virus replicates . . . it's a race between the vaccine and the virus."

Ramachandruni said that with larger viruses such as COVID-19, its size gives it more stability. For example, in a small virus, the part that can make you sick may only be a small part of its overall structure. While in a small virus, the entire structure of a virus has the ability to infect a patient.

So if a small virus mutates, the likelihood that the whole virus mutates is very high, while in larger viruses, it's a craps shoot. Whether it mutates or not depends on whether the change happened in a part of the virus that is infectious.

"But here -- the COVID variant -- what happens is you get the COVID vaccine or you develop an immunity, the virus comes into your body, your body recognizes it," he said. "It'll have time to act for five days."

COVID-19 drive-thru clinic set Friday in Corpus Christi
COVID-19 drive-thru clinic set today in Corpus Christi at the Old Christus Spohn Hospital Memorial site.

When herd immunity is reached, a virus can become endemic, or localized in pockets of unvaccinated people. From there, it is much easier to manage than a pandemic.

"The majority of the community needs to have antibodies in order to control the transmission of this virus and allow it to become endemic," said Corpus Christi-Nueces County Public Health Director Annette Rodriguez. "It will never become endemic if the transmission is so high that new variants continue."

Public health officials said herd immunity could be reached if 85 percent of a population is vaccinated against the COVID-19 virus. Currently, only 55 percent of Nueces County residents are vaccinated.

Driscoll Children's Hospital Infectious Diseases specialist Dr. Jaime Fergie said the Delta variant currently accounts for 99 percent of COVID-19 infections locally.