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Delta variant: why the second dose is so important?

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Kamal Saini
Kamal S. has been Journalist and Writer for Business, Hardware and Gadgets at Revyuh.com since 2018. He deals with B2b, Funding, Blockchain, Law, IT security, privacy, surveillance, digital self-defense and network policy. As part of his studies of political science, sociology and law, he researched the impact of technology on human coexistence. Email: kamal (at) revyuh (dot) com

Most vaccinations against Sars-CoV-2 only develop their full effect when a second dose is injected after several weeks. Because of the Delta variant, the second dose is now even more important. But why is that and how many people have already missed their second vaccination?

The immune system needs this second round of training to really arm itself against the coronavirus – this is especially true for the new variants. 

But more than five million people, or nearly 8 per cent of those who got a first shot of the Pfizer or Moderna vaccines, have missed their second doses, according to the data from the Centers for Disease Control and Prevention. 

This endangers them personally just as much as it jeopardizes the hard-won successes in fighting pandemics.

Millions miss the second dose

Some may hesitate because they have experienced unpleasant side effects such as fever and body aches after the first vaccination. 

For others, going back to the doctor or vaccination center is too tedious – or the appointment doesn’t fit into their private plans. 

Or they feel safe after the first dose – a fallacy that may also have been promoted by the fact that experts in recent months already attested a certain protective effect to the first vaccination.

The second syringe makes the difference

But that was true of the so-called wild form of the corona virus, which was rampant at the time. In the meantime, however, this has been suppressed by mutations, for which this statement can no longer be held. 

First, because there is simply not enough data on this yet. 

Second, however – and this is the greater concern – because, according to initial observations, the first vaccination against the more contagious Delta variant, which is also spreading rapidly in the US, has not yet developed a sufficient protective effect.

This also applies, for example, to the mRNA vaccine from BionTech / Pfizer, which is the most widely used in the United States. 

In the journal magazine Lancet, British researchers report that around four weeks after the first vaccination, 68 percent, i.e. a good two thirds of the study participants, showed weak antigen neutralization compared to the delta variant. 

With the other strains, it was only 21 per cent (approx. one-fifth), with the alpha mutation around 50 per cent. Those who were vaccinated for the first time would therefore have a high risk of contracting the Delta variant anyway – and of infecting the people around them.

Two doses of vaccine also keep Delta in check

A full vaccination, on the other hand, also offers highly effective protection against Delta. This was the result of another study, this time initiated by the British public health authority Public Health England (PHE). Hospital stays were therefore required in significantly less than ten per cent of cases for those who had been completely vaccinated with AstraZeneca or BionTech / Pfizer.

The protection against symptomatic courses is only slightly lower for fully vaccinated persons after contact with the delta variant than with the coronavirus original form: After a BionTech / Pfizer vaccination, 88 per cent were protected against the delta variant, 93 per cent against the alpha variant. Those who have been vaccinated twice with AstraZeneca are 60 percent protected against diseases with the delta variant and 66 percent with the alpha mutation.

Protection fades faster after just one vaccination

The protective effects determined only apply to comparatively freshly vaccinated people. Over time, the protective effect of the vaccination decreases significantly. 

The antibodies, which form the first bulwark against the virus, disappear relatively quickly from the blood. When the virus comes into contact with the virus, another actor in the immune system is called upon: the immune memory.

If the vaccine was only vaccinated once, the immune protection could wane even faster. According to a virologist:

With the second vaccination, you reach the immunological memory. This means that the antibody response becomes stronger again after the second vaccination, ten times stronger, twenty times stronger. You have a longer effect.

Double training, longer effect

To put it simply: Similar to how everyone can remember better when they repeat the learning material, the immune system can also remember the virus better after the second dose. 

“It’s an exercise for the immune system to become even more precise – and faster,” say experts.

This could also apply to the Johnson and Johnson vaccine, for which only one vaccine dose is provided so far. 

In view of the new mutations, a second vaccination may also be required here, possibly with a different vaccine. 

However, not enough data is currently available on this.

Photo by Ben Hasty/MediaNews Group/Reading Eagle via Getty Images

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