At a time when it started to look like we might be nearing the end of the coronavirus, the Omicron variant took the world by storm. It is a completely new variant of the coronavirus not based on previous strains characterized by numerous mutations in the spike protein gene. Other variants sport similar mutations many of which have been associated with the ability to spread faster or bypass immunity.

What do we know about the Omicron variant?

The Omicron variant spreads much more effectively than its predecessors. Its R0 is believed to be ten (compared to a score of just two or three for the original Wuhan variant). Cases exploded in South Africa, followed by Denmark, United Kingdom, France and other European and North American countries.

Despite flight bans, the virus has spread to all corners of the world by today. Unlike in South Africa, where Omicron arrived at a time when the Delta strain had all but receded, it hit Europe when Delta was still rising.

Omicron has become the predominant viral population in many countries by today, while it remains unclear whether it has the potential to become completely dominant as the Delta variant has over the last five months.

It needs to be kept in mind that countries' situations cannot be compared based on international databases alone. Countries that rely heavily on testing report more cases as they also diagnose those who only carry the virus or exhibit minimal symptoms. For example, Denmark analyzes approximately 250,000 PCR tests and another quarter of a million antigen tests every single day.

The Omicron variant is adept at bypassing immunity. Both people who have recovered from Covid and those who have been fully vaccinated are much more likely to catch the strain compared to the Delta variant. Still, a drop in the effectiveness of vaccines was recorded before the arrival of Omicron.

The level of protection against Omicron offered by vaccines drops to a very low level four or five months after the second shot, with some studies suggesting it disappears altogether. However, vaccines remain highly effective in preventing severe illness and death, while booster doses quickly restore the efficacy of immunization (to 75-80 percent). Even if vaccinated people are infected, they experience milder or even asymptomatic Covid. The importance of vaccines in managing COVID-19 has, therefore, not been reduced.

The Omicron strain causes a milder case of the disease. The principal symptoms are a runny or stuffy nose, mild fever and less often disruptions to the senses of taste and smell. This means that getting tested to avoid spreading the SARS-CoV-2 virus makes sense even if one is merely experiencing mild cold symptoms.

Both data out of South Africa and studies carried out in the UK show that the risk of hospitalization is down 40 percent compared to the Delta strain, while people also spend less time in the hospital on average. This is not enough to suggest we will not see a spike in hospitalizations, however, as the new variant's contagiousness might mean more people will be infected.

The effect of the Omicron strain reaching the elderly part of the population remains unclear, especially in the case of people who are unvaccinated or have gone longer than six months since receiving the last shot.

UK data suggests hospitalization has grown the most in the 85+ age group and slightly in the 65-84 age group, meaning that Omicron might not be milder for elderly people. The number of people whose PCR test comes back positive but who are not suffering from the coronavirus has also grown.

While the strain might not put people in the hospital, several countries have noted that its rapid spread is having an effect on services, including in healthcare. People are forced to isolate and miss work due to very mild symptoms or being close contacts of diagnosed persons that is causing staff shortages. That is one reason many countries are revising their isolation and quarantine requirements.

This approach is made possible by the Omicron variant's shorter incubation period. For example, South Africa has lifted the self-isolation requirement and is only testing and isolating those with symptoms.

The U.S. has shortened the isolation period to five days, while several other countries have settled on seven. Different states have different rules, with some requiring a negative test result to end isolation and others not. Experts lack consensus on the duration of isolation and quarantine as well as the criteria for ending it.

Are vaccines useful?

This question is hardly surprising looking if only at Estonian statistics where approximately 50 percent of daily cases are in vaccinated people. But if we adjust the number of cases to population, we see that infection is twice as likely for unvaccinated people.

We must not forget that vaccines are mainly meant to avoid severe illness and death, not necessarily infection and mild cases. The effectiveness of mRNA vaccines at preventing severe illness is 70 percent without a booster dose and more if an additional shot has been administered in the case of the Omicron variant.

The effectiveness of vaccines falls over time, especially their ability to prevent mild illness. Recent Omicron studies suggest that people who are vaccinated experience milder cases, are less likely to require hospitalization and intensive care or die as a result of the virus. Therefore, vaccines remain the surest way to exit the pandemic.

Like all medicines, vaccines sport side-effects, and while they are predominantly mild and short-term, serious consequences have been reported in isolated cases. Effective vaccination seems to require three doses instead of two, while we do not know how often booster doses will be needed. Other measures, such as masks, social distancing and good ventilation, must also stay with us for the time being.

What will happen next?

The appearance of the Omicron variant of the coronavirus suggests the latter is running out of steam as immunity continues to grow either through vaccination, recovery or a combination of both. That is why while we are seeing a considerable number of new cases, they have not translated into an increased mortality rate or overload of the medical system.

Once a large part of the population has been vaccinated and severe illness and death avoided, it will no longer be necessary to test asymptomatic people or isolate close contacts. Continued infection that will not result in severe cases is a very likely scenario moving forward, while this will contribute to more robust immunity and protection against future infection.

That would allow us to add SARS-CoV-2 to the list of seasonal viruses that while causing respiratory symptoms do little to disrupt people's everyday lives.

Still, I believe the World Health Organization is right to suggest that nothing is over until everything is over. The world still has counties sporting very low vaccination and likely also infection rates. New strains of the virus can still develop in such places, while it is to be hoped they will not be as effective at spreading and causing severe illness.

Covid vaccinations will also stay with us for some time to come. The questions of who should be vaccinated, with what and how often need to be answered by future research. While there will surely be new vaccines, I doubt they will be able to completely take the virus out of circulation. If recovering from the virus fails to grant lifelong immunity, I doubt vaccines can. However, it is quite likely that every new case of the coronavirus will be milder than the last.

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