PANDEMIC

How will the covid pandemic end?

How the pandemic ends will vary from country to country. It will largely depend on the number of vaccinated people and on how many cases of infection there have been (natural immunity) since the beginning of the pandemic

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Photo: Shutterstock
Photo: Shutterstock
Disclaimer: The translations are mostly done through AI translator and might not be 100% accurate.

After more than 18 months of the pandemic, with social distancing measures, wearing masks and occasional quarantine, what we want to know more than anything is when and how it will all end. Although nothing is certain, there is a lot of evidence that gives us some realistic expectations about how the pandemic will progress over the next year.

Covid-19 is not the first coronavirus to cause a huge global pandemic. It is speculated that the "Russian flu" that appeared in 1889 was not actually the flu but was caused by a different type of coronavirus, OC43.

The Russian flu pandemic caused four or five waves of illness over the next five years, after which it seemed to disappear. In England and Wales, most of the deaths occurred between 1890 and 1891. A variant of the OC43 virus, the potential cause of that pandemic, is still circulating today, although it rarely causes serious illness.

Current evidence suggests that SARS-CoV-2, the coronavirus that causes Covid-19, will remain with us. Many scientists dealing with this virus came to this conclusion a few months ago. Neither a vaccine nor a natural infection will prevent the spread of the virus.

Although vaccines reduce transmission, they do not prevent infection sufficiently to eradicate the virus. Even before the delta strain of the virus appeared, we had cases of people with two doses of the vaccine becoming infected and passing it on to others. Since vaccines are somewhat less effective against the delta strain compared to other forms of the virus, the possibility of infection after vaccination has also increased.

Immunity also begins to wane a few weeks after receiving the second dose of the vaccine. And since immunity is neither complete nor permanent, herd immunity is unachievable. This means that Covid-19 is likely to become endemic, with the rate of infection depending on the rate of immunity and the interaction of the population.

Other types of coronaviruses that attack humans cause recurrences of infection every three to six years on average. If SARS-CoV-2 behaves in the same way, it would mean that e.g. in Great Britain every year on average could infect between one sixth and one third of the population, that is between 11 and 22 million people, or 30 to 60 thousand per day. This is not as scary as it sounds though.

New research (which is still awaiting verification and review by fellow scientists) indicates that immune protection against the development of symptomatic Covid-19 is weakening. However, protection against severe disease - caused by immunization or natural infection - is significantly more durable, and does not seem to be lost when faced with new variants.

The vast majority of infections with other types of coronaviruses are either asymptomatic or, in the worst case, like a mild cold. There are signs that Covid-19 could end up the same way.

A pandemic with multiple possible endings

How the pandemic ends will vary from country to country. It will largely depend on the proportion of vaccinated people and how many cases of infection there have been (and consequently how much natural immunity has been built up) since the beginning of the pandemic.

In the UK and other countries with high vaccination coverage and a high number of past infections, most people will have some form of immunity to the virus. For example, in England, it is estimated that at the beginning of September, more than 94% of the adult population had antibodies to Covid-19.

Among those with previously acquired immunity, Covid-19 has been shown to be less severe. And as the immunity of as many people as possible strengthens over time, we can expect that an increasing proportion of new cases of infection will be asymptomatic or, in the worst case, cause a mild illness. The virus will stay with us, but the disease will become part of our history.

On the other hand, in countries without many cases of previous infection, even with high vaccination rates, many will remain susceptible to more serious forms of the disease. Even in countries with the highest vaccine coverage in the world, more than 10% of people have yet to receive the vaccine. Almost everyone who is not vaccinated is likely to contract the virus. Once infected, they will be at the same risk of severe illness and death (depending on their age and health status) as at any time during the pandemic.

In those countries, loosening the measures and opening up will almost certainly lead to an exponential growth of infection, due to the large number of people without immunity. As the amount of virus in circulation increases, there will be more and more cases in vaccinated people, given that vaccines are not 100% effective. Although Covid-19 tends to be less severe in vaccinated people, some still get seriously ill, so in those countries it may happen that a significant number of vaccinated people need hospital care.

When the decision to ease measures and reopen in these countries will be made will also be crucial. If it is too early, many people will still be waiting for vaccination at that point. If it is too late, the effectiveness of the vaccine in those already vaccinated may begin to decline.

Still, the key lesson of the Russian flu is that Covid-19 will become less relevant in the coming months, and that most countries are almost certainly over the worst of the pandemic. However, it is still extremely important that the vaccine is available to the remaining, vulnerable populations around the world.

It is becoming clear that the main effect of vaccination will not be to prevent people from contracting the SARS-CoV-2 virus, but to reduce the severity of infection upon first encounter with the virus. For those who have already experienced a first or second natural infection, vaccines will provide a relatively small level of additional protection. In order to ensure the greatest possible reduction in severe disease symptoms, vaccines need to be offered to as many people as possible, now.

The author is a professor of medicine, expert in infectious diseases, specialized in medical microbiology and virology; he is a member of the WHO advisory boards for the global response to the pandemic

(The Conversation; digitalnademocracija.com)

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(Opinions and views published in the "Columns" section are not necessarily the views of the "Vijesti" editorial office.)