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In the early days of the pandemic, herd immunity was put forward as one of the ways to deal with the COVID-19 pandemic.

Sweden famously led the pack on this one, but have recently reassessed that decision, toughening their approach in an attempt to ward off a resurgence of infections.

Herd immunity is reached when the majority of any given population (70% to 90%) becomes immune to a virus, either because they have become infected and recovered, thereby building up antibodies, or through vaccination.

When that happens, the disease is less likely to spread to people who aren’t immune, because there just aren’t enough infectious carriers to reach them.

It’s a good idea in theory, but when it comes to COVID-19, nothing is certain.

It’s an unpredictable disease, and we’re only now getting to grips with whether or not the antibodies produced after recovery stick around long enough to prevent reinfection.

This brings us to recently released research conducted at Imperial College London, which claims that immunity could be shortlived, making it the latest study to cast doubt on the idea that any community could develop herd immunity.

The Financial Times explains that the study claims that the immune system responds to COVID-19 in a similar way to its response to the flu and other coronaviruses.

Wendy Barclay, co-author and head of the department of infectious disease at Imperial, said:

“What we do know is that seasonal coronaviruses that circulate every year can reinfect people after six to 12 months and we suspect that the way the body reacts to these coronaviruses is similar.”

The research also raises questions as to how long the vaccine would last. At the same time, a good vaccine would be better than herd immunity.

The researchers tested more than 365 000 adults over five months, finding a decline in antibody levels in all age groups. Participants in the study were tested in three phases: June to July, July to August, and September.

Over this time, the smallest drop in antibodies occurred amongst younger people, while the elderly experienced the largest drop.

“These data suggest the possibility of decreasing population immunity and increasing risk of reinfection as detectable antibodies decline in the population,” said the study, which has not yet been peer-reviewed.

“This is a really big challenge to the idea that herd immunity can be achieved through natural immunity,” said Helen Ward, co-author and professor of public health at Imperial.

This isn’t that surprising if you consider that the common cold, or the flu, has a habit of coming back at least twice a year, which suggests that we never really build up a lasting immunity to it. There’s a reason that you go for a ‘flu shot’, every year.

If you’re keen to see whether or not you have COVID-19 antibodies, here’s how.

For the foreseeable future, even if you show signs of having built up antibodies, you can’t rely on them to immunise you to a second infection.

Mask up, wash your hands, and keep physically distancing.

Failing this, we could be looking at a second hard lockdown in South Africa, and nobody wants that.

[source:financialtimes]