"Studies have demonstrated conclusively that the strongest immunity against Omicron is the so-called hybrid immunity – three doses of the vaccine plus having had the infection. For people who have not had Covid, two doses of the vaccine aren't very efficient. What is necessary is three doses," virologist and associate professor at the Faculty of Medicine's Institute for Microbiology and Immunology Ana Banko said in her interview with Kurir.

Does the hybrid immunity protect us regardless of the fact that the vaccines were made for the previous strains and no matter when they were taken and when someone got infected?

"Twenty percent of those who have taken three doses of the vaccine got infected, and only 6.9 percent of those who have taken four. This is the data from the scientific studies which clearly shows that the increase in the number of doses, regardless of the fact that these vaccines were not made specifically for Omicron, results in a higher efficiency of the vaccine. So, although they are far less efficient than at the beginning of the immunization – as the virus is different – they are still efficient. Furthermore, Japan, where 90 percent of the elderly people have taken three doses, has a mortality rate of 0.3 percent, whereas in the US and the UK, where this vaccination rate stands at 30 percent, the mortality rate reaches 1.1 percent. As for how long immunity lasts, that depends on the individual, and we cannot measure it precisely."

What about by measuring antibodies?

"Unfortunately, that is irrelevant now. Earlier, we had evidence – with Delta, for example – that a high antibody titer is correlated with efficiency, and that could be used as a measure of immunity. However, with the current coronavirus variants, the antibody level does not correlate with whether the immunity will be sufficient or more or less efficient. Here, as in Europe and globally, the BA.5 Omicron subvariant is dominant, and its unique characteristic is the mutations which are defined in the literature in English as an 'immunity wall'. As a result, what happens is the so-called immunity breakthrough, so even those who have had subvariant BA.1 or BA.2 can get infected with it. This is why it is important that those who have not taken the vaccine and got infected with BA.1 or BA.2 should know that they can get infected with both BA.4 and BA.5. With BA.1 and BA.2, the natural immunity in those who haven't been vaccinated isn't considered important, as it is the weakest compared to the immunity developed as a result of the previous variants. Even though there were fears that the BA.2.75 subvariant, known as Centaurus, will prevail over BA.5, it didn't happen. Centaurus is risky as it forms stronger bonds with our cell receptors, but it evidently does not have the transmission and population survival capacity as BA.5"

'THE ELDERLY AND THE VULNERABLE OUGHT TO GET TESTED IMMEDIATELY'

When should you get tested? Is it justified to do it every time you have a runny nose and a sore throat?

"You should get tested depending on the intensity and the symptoms, as well as on whether you know you have been in contact with someone infected. A positive test doesn't necessarily mean being successfully treated for the disease, but it suggests how to behave in the environment. At any rate, you can act responsibly and not spread the virus even without a test. If you must go to work or have other sorts of contacts, and you want to be sure that you won't spread the virus, it makes perfect sense to get tested. It is important for the elderly and for those with chronic associated diseases to get tested in order to receive the antivirus therapy in time."

The antivirus therapy, specifically Paxlovid, caused US President Joseph Biden to get re-infected. Did that come as a surprise to you?

"No, because it has been shown that Paxlovid prolongs viremia. That said, there are certainly more benefits than drawbacks to this medication, the same being the case with the other antiviral drug – Molnupiravir."

Are we too late for the fourth dose, bearing in mind that this seventh wave is already high?

"No, especially those who haven't had the infection and who are fairly careful. The general guideline is that those older than 50, as well as those younger but with chronic associated diseases, should get the fourth dose. The fourth dose isn't necessary for people who are younger and healthy, especially those who have the hybrid immunity. This is because Omicron, all its bad characteristics notwithstanding, i.e. better transmissibility and the immunity breakthrough, still has a milder clinical presentation of Covid. A SARS-CoV-2 infection can make an already existing condition more complicated for those people who have a chronic illness or are elderly, who as a rule have a poorer immune response. This is evident if you take a look at the profiles of the patients who are currently in Covid hospitals."

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Foto: privata arhiva

How long will this wave last and how high will it go?

"I don't expect the wave to last long, as the virus is spreading unhindered among people, without any obstacles whatsoever, so the majority of the population will be infected quickly."

How many official infections could we have?

"No number would surprise me, but the real number of infections is far bigger than the official one. Many don't get tested, many others carry the virus asymptomatically, and still others do home tests, which aren't entered into the official database."

Will Serbia reach herd immunity in this seventh wave, with Omicron as the most infectious virus so far, as some claim?

"One of the most infectious viruses is the measles virus, where one infected person can infect up to 18 unvaccinated people. We cannot yet say SARS-CoV-2 is like the measles, but of all the coronavirus variants so far, BA.5 is the most potent in this respect."

foto: Shutterstock

LIVING WITH CORONA

Will there be an end to the pandemic?

"That depends on many factors. One is the virus that keeps changing, another is the lifestyle and the dynamic of our movement, which is not limited now. The final factor is the human being. Those who are infected or suspect they might be should make sure not to spread the virus any further – by isolating themselves (staying at home or wearing an N95 face mask in very brief contacts when they need to go to the shops, etc.). This isolation, or rather caution, should last for about 10 to 15 days. That is key in making sure others don't get infected. As for the virus, one day it will be considerably weaker, but that takes time."

How long?

"The coronaviruses which cause mild infections, which were known to us even before the pandemic – the four viruses that cause the common cold – have most probably been in circulation in humans between 150 and 800 years. One of the last pandemics was the 1889 one, and it lasted two years. So, it takes time for humans and the coronavirus to adapt to the symbiosis."

This coronavirus will live on among us?

"It is possible, but not certain. However, it doesn't really matter. What matters is that this virus infection becomes clinically insignificant and mild, but that takes time."

Can you at least try to estimate when the pandemic will be declared over? Could the virus surprise us again and produce powerful mutations such as Delta?

"The tendency is obvious to get milder but more transmissible variants. When the pandemic will be declared over will be more based on the number of hospitalizations and deaths than new infections."

Is there an ideal time to get infected? Is it now, with BA.5, which causes mild symptoms?

"There is no ideal time to get infected because we don't know if the mild symptoms will be followed by long Covid, which occurs in nearly 20 percent of those infected. The data indicates that as much as 76 percent of those suffering from the so-called long Covid have had a mild clinical presentation of the acute disease. The explanation for the long Covid symptoms is that you get infected with SARS-CoV-2 in places outside of the respiratory tract, e.g. the digestive tract, the nervous system, or blood. Although the respiratory swabs may come up negative, such a person can have long-lasting diarrheas, headache, or a weaker mental focus, etc. The most recent Harvard study has shown conclusively that, for example, people with long Covid still have virus elements in their blood, unlike the control group, made up of subjects who had had Covid, but didn't report symptoms of long Covid."

How long does it last?

"Long Covid can last three months and more; with some people, longer than a year even. This is why it's important to know that the virus can survive in other tissues, where, among other things, its S-protein is synthesized, which stimulates our immune system over a prolonged period of time. Tissue and organ damage can occur in these places, and an autoimmune process or a superantigen effect – as we refer to it in immunology – can develop, as a result of which the immune system might react excessively to a different infection or disease. One example is the infamous mysterious acute hepatitis in children, which, according to the studies, occurs in children who had Covid 74 days prior on average. It has been shown that the SARS-CoV-2 virus remained in their digestive tracts two to three months after they'd had Covid, stimulating their immune system. The immune system then reacted to a different infection, e.g. an adenovirus one, excessively, causing hepatitis. Many of those children needed a liver transplant."

foto: Shutterstock

'MONKEYPOX NOT A CAUSE FOR CONCERN, BUT SHOULD BE MONITORED'

Should we be concerned about monkeypox, and can the two pandemics combine?

"The synergistic effect of these two viruses in an individual is almost impossible. Monkeypox isn't a disease to be concerned over, but to be cautious about and monitor. The virus didn't leave Africa for a long time, but now it is appearing simultaneously across the world, and there are more cases confirmed in the laboratory than we had seen before outside of Africa. Still, the mortality rate is low – four cases up until now. However, they were people with associated diseases, such as lymphoma. This is still a virus infection that we have seen before – it can cause complications, but it can also be treated and prevented."

'THERE AREN'T MANY MUTATIONS'

Does such a high number of coronavirus mutations surprise you?

"No, this virus actually doesn't have very many mutations, it's just that the pandemic has been going on for too long, and the virus is moving through too many hosts. The flu changes much more. Or hepatitis C and HIV, against which a vaccine hasn't even been made because they mutate to an extraordinary extent. The key number of mutations in Omicron, compared to the previous strains, is 30-ish in the S-protein region. It is these changes that have reduced the possibility of causing more severe clinical presentations by Omicron."

What would happen to us if there were many mutations?

"We don't know that, but perhaps the virus would destroy itself because it would produce so many errors that it could no longer survive in the human population."

'THE NEW VACCINE – A RACE AGAINST TIME'

Do you expect much from the new vaccine?

"There are speculations that it might be ready by the end of the year, but the question is which subvariant it is made for. What we have is a race against time – if adapting vaccines for Omicron subtypes will be fast enough when a new variant becomes prevalent. An Omicron vaccine would be ideal, not one for individual subvariants."

Do you also think, as some medical doctors do, that we could take the jab every three months?

"In this context, I believe that once a year is enough, if we make the comparison with the flu virus. It would do no harm if everyone were to take the vaccine, not only the vulnerable groups, but it isn't necessary now, because Omicron mostly causes a milder clinical presentation."

Kurir.rs/Jelena S. Spasić

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