ec7fa8a17afb4ed09668ca3cba134dcd Why some may need just one vaccine shot
Why some may need just one vaccine shot Does a coronavirus infection make you immune? For a long time, there was no clear answer. The big question was – how long does immunity last? Because Covid is still a relatively new disease, all we can say even now is that past infection seems to protect people for a few months. Does that mean they don’t need vaccines? No. There have been some confirmed cases of re-infection, and it is increasingly looking like two new variants of the coronavirus in Brazil and South Africa are able to dodge old immunity. So, people with a past infection still need vaccination. But do they need the full course of two shots, or will one be enough? This is a very important question right now as vaccines are in short supply. If past patients can do with just one shot, it frees up many millions of doses for others. For instance, the latest sero survey in Delhi shows more than half the population has Covid antibodies. In the US, up to a third of the population may have coronavirus antibodies by now. If all of those people need just one dose each, others can be vaccinated faster. medium80670754 ‘ALREADY PRIMED’ When you take two doses of a vaccine, the first is said to ‘prime’ the immune system, and the second is said to ‘boost’ it. Now, research by scientists at the Icahn School of Medicine at Mount Sinai New York suggests people with a past infection are already primed. Although the study published in medRxiv is based on a small sample and has not been peer reviewed, its findings are interesting and important. For their research, the Icahn School team looked at 109 people, of whom 41 had coronavirus antibodies and 68 didn’t. When they took their first dose of an mRNA vaccine (the only type approved in the US), those with antibodies responded better than those who had not been infected before. “Majority of seronegative (no coronavirus antibodies) individuals mount variable and relatively low SARS-CoV-2 IgG responses within 9-12 days after vaccination. In contrast, individuals with pre-existing SARS-CoV-2 immune responses (as evidenced by SARS-CoV-2 antibodies) rapidly develop uniform, high antibody titers within days of vaccination,” the study says. The difference between the two sets of immune responses was huge. After the first dose, people with a past infection, had 10-20 times higher concentrations of antibodies than the others. What’s more, they remained ahead even after the other group took its second dose. “Antibody titers of vaccines with pre-existing immunity are not only 10-20 times higher than those of naïve vaccines at the same time points, but also exceed the median antibody titers measured in naïve individuals after the second vaccine dose by more than 10-fold.” The scientists say, it seems that for someone with a past infection the first vaccine dose is the equivalent of a second dose. “Changing the policy to give these individuals only one dose of vaccine would not negatively impact on their antibody titers, spare them from unnecessary pain and free up many urgently needed vaccine doses,” they say. At this point, there isn’t enough evidence for governments to change vaccination guidelines based on these findings, but if follow-up studies show the results hold – and not just for mRNA vaccines – this idea could be a game changer. KNOW YOUR ANTIBODIES Covid has made ‘antibody’ an everyday word. But even after months of seeing it in the papers, our understanding of what antibodies are and how they work remains foggy. A new Wired article by Roxanne Khamsi (May I borrow your Covid immunity), reveals antibodies in sharp detail. “Antibody molecules are Y-shaped, and their tips have nooks and crannies that can lock onto specific viruses or bacteria,” she says. Think of them as cleft sticks that serve as germ catchers. While we have spent the past year worrying about just one kind of germ – the coronavirus – your immune system makes a mind boggling variety of antibodies. “The average person has billions of B cells that can produce somewhere between 9 and 17 million distinct antibodies,” says Khamsi. But that’s not even half the story. “Humans have the potential to generate 1,000,000,000,000,000,000 (1 quintillion or million-trillion) different kinds of antibodies,” she says citing research by scientist Dennis Burton. Try wrapping your mind around that.



Why some may need just one vaccine shot



Does a coronavirus infection make you immune? For a long time, there was no clear answer. The big question was – how long does immunity last? Because Covid is still a relatively new disease, all we can say even now is that past infection seems to protect people for a few months. Does that mean they don’t need vaccines?

No. There have been some confirmed cases of re-infection, and it is increasingly looking like two new variants of the coronavirus in Brazil and South Africa are able to dodge old immunity. So, people with a past infection still need vaccination. But do they need the full course of two shots, or will one be enough?

This is a very important question right now as vaccines are in short supply. If past patients can do with just one shot, it frees up many millions of doses for others. For instance, the latest sero survey in Delhi shows more than half the population has Covid antibodies. In the US, up to a third of the population may have coronavirus antibodies by now. If all of those people need just one dose each, others can be vaccinated faster.


‘ALREADY PRIMED’

When you take two doses of a vaccine, the first is said to ‘prime’ the immune system, and the second is said to ‘boost’ it. Now, research by scientists at the Icahn School of Medicine at Mount Sinai New York suggests people with a past infection are already primed. Although the study published in medRxiv is based on a small sample and has not been peer reviewed, its findings are interesting and important.

For their research, the Icahn School team looked at 109 people, of whom 41 had coronavirus antibodies and 68 didn’t. When they took their first dose of an mRNA vaccine (the only type approved in the US), those with antibodies responded better than those who had not been infected before.

“Majority of seronegative (no coronavirus antibodies) individuals mount variable and relatively low SARS-CoV-2 IgG responses within 9-12 days after vaccination. In contrast, individuals with pre-existing SARS-CoV-2 immune responses (as evidenced by SARS-CoV-2 antibodies) rapidly develop uniform, high antibody titers within days of vaccination,” the study says.

The difference between the two sets of immune responses was huge. After the first dose, people with a past infection, had 10-20 times higher concentrations of antibodies than the others. What’s more, they remained ahead even after the other group took its second dose.

“Antibody titers of vaccines with pre-existing immunity are not only 10-20 times higher than those of naïve vaccines at the same time points, but also exceed the median antibody titers measured in naïve individuals after the second vaccine dose by more than 10-fold.”

The scientists say, it seems that for someone with a past infection the first vaccine dose is the equivalent of a second dose. “Changing the policy to give these individuals only one dose of vaccine would not negatively impact on their antibody titers, spare them from unnecessary pain and free up many urgently needed vaccine doses,” they say.

At this point, there isn’t enough evidence for governments to change vaccination guidelines based on these findings, but if follow-up studies show the results hold – and not just for mRNA vaccines – this idea could be a game changer.

KNOW YOUR ANTIBODIES

Covid has made ‘antibody’ an everyday word. But even after months of seeing it in the papers, our understanding of what antibodies are and how they work remains foggy. A new Wired article by Roxanne Khamsi (May I borrow your Covid immunity), reveals antibodies in sharp detail.

“Antibody molecules are Y-shaped, and their tips have nooks and crannies that can lock onto specific viruses or bacteria,” she says. Think of them as cleft sticks that serve as germ catchers.

While we have spent the past year worrying about just one kind of germ – the coronavirus – your immune system makes a mind boggling variety of antibodies. “The average person has billions of B cells that can produce somewhere between 9 and 17 million distinct antibodies,” says Khamsi.

But that’s not even half the story. “Humans have the potential to generate 1,000,000,000,000,000,000 (1 quintillion or million-trillion) different kinds of antibodies,” she says citing research by scientist Dennis Burton. Try wrapping your mind around that.


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