By Julie Steenhuysen

CHICAGO (Reuters). The Omicron virus is spreading much faster than other coronaviruses, but it’s unlikely that countries will achieve “herd immunity to COVID-19”, which means enough people become infected to stop the virus from spreading, according to leading experts.

    From the earliest days of the pandemic, public health officials have expressed hope that it was possible to achieve herd immunity against COVID-19, as long as a high enough percentage of the population was vaccinated or infected with the virus.

As the coronavirus developed new mutations over the last year and was able to infect previously vaccinated people, those hopes fell apart.

Omicron was discovered late last year and some officials in the health sector have revived herd immunity.

Their argument is that due to its rapid spread, the variant could cause milder disease and expose more people to it.

Disease experts note, however, that Omicron’s transmissibility is aided by the fact that this variant is even better than its predecessors at infecting people who were vaccinated or had a prior infection. This further supports the belief that coronaviruses will find new ways to penetrate our immune systems, experts said.

“Reaching a theoretical threshold beyond which transmission will cease is probably unrealistic given the experience we have had in the pandemic,” Dr. Olivier le Polain, an epidemiologist with the World Health Organization (WHO), told Reuters.

This does not mean that previous immunity is useless. Reuters spoke to many experts that, instead of herd immunity and vaccines, prior COVID-19 infection was increasing in evidence. They said this would increase population immunity which, in turn, makes the disease much less severe for those already infected.

    “As long as population immunity holds with this variant and future variants, we’ll be fortunate and the disease will be manageable,” said Dr. David Heymann, a professor of infectious disease epidemiology at the London School of Hygiene and Tropical Medicine.

MEASLES ARE NOT FOR YOU

The COVID-19 vaccines are primarily intended to protect against severe illness and death, rather than infecting. Clinical trials in 2020 showed that only two vaccines were more effective than the others against the disease. This led to hope that widespread vaccination could help contain the epidemic.

    With SARS-CoV-2, two factors have since undermined that picture, said Marc Lipsitch, an epidemiologist at Harvard T.H. Chan School of Public Health.

    “The first is that immunity, especially to infection, which is the important kind of immunity, wanes quite quickly, at least from the vaccines that we have right now,” he said.

    The second is that the virus can quickly mutate in a way that enables it to elude protection from vaccination or prior infection – even when immunity has not waned.

    “It changes the game when vaccinated people can still shed virus and infect other people,” said Dr. David Wohl, an infectious disease specialist at the University of North Carolina at Chapel Hill School of Medicine.

It is important to remember that Omicron can cause infection, which could increase the risk of developing the next type. Wohl suggested that Omicron may have protected you from becoming Omicron-infected again. 

    Vaccines in development https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-is-wake-up-call-covid-19-vaccine-developers-2021-12-08 that provide immunity against future variants or even multiple types of coronaviruses could change that, said Pasi Penttinen, the top influenza expert at the European Centre for Disease Prevention and Control, but it will take time.

    Still, the hope for herd immunity as a ticket back to normal life is hard to shake.

    “These things were in the media: ‘We’ll reach herd immunity when 60% of the population are vaccinated.’ This didn’t happen. Then, for 80%. Again, it didn’t happen,” Francois Balloux, professor of computational systems biology at University College London, told Reuters.

“As horrible as it sounds, I think we have to prepare ourselves to the fact that the vast majority, essentially everyone, will get exposed to SARS-CoV-2,” he said.

Experts in global health believe that coronavirus may eventually become an endemic virus, spreading persistently throughout the population. This could also lead to sporadic outbreaks. Omicron has risen, but there are questions as to when this might occur.

“We will get there,” said the WHO’s le Polain, “but we are not there at the moment.”