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How effective is a single vaccination against COVID-19?



Cases are starting to take place.

When Colin Horsman, 85, was admitted to Doncaster Royal Hospital in late December, it was suspected of having a kidney infection. But shortly thereafter, he was infected with COVID-19 – at that time about one in four people in the hospital who had the virus had been exposed to the virus. He had a serious condition and eventually had to wear a ventilator. A few days later he died.

At first glance, Horseman’s situation may seem pretty normal. But it’s not sad for this. After all, at least 84,767 people have died from the disease in the UK alone at the time of writing. But as his son described in the local newspaper less than three weeks earlier, he was among the first in the world to receive the initial dose of the COVID-1

9 vaccine, the Pfizer-BioN version. Tech, he was scheduled to get a second dose two days before his death.

In fact, most vaccines require a booster dose to work.

MMR – the measles, mumps, and rubella vaccine, which is given to infants worldwide, is used to protect against life-threatening childhood infections.About 40% of people who received a single dose were not protected from all three viruses. Compared with 4% of those who received a second time. People in the same group were four times more likely to develop measles than the latter and had an outbreak in places where large numbers of people did not complete their MMR vaccination schedule.

“The reason people are so keen on the stimulation and think they are so important is that they send you into all of these other granular immune response modes,” said Danny Altmann, professor of immunology at Imperial College London.

How do booster vaccines work?

When the immune system first encounters a vaccine, it activates two important white blood cells. The first is the plasma B cells, which primarily focus on producing antibodies. Unfortunately, these types of cells are short-lived, so although your body may swim in the antibody in just a few weeks, without a second shot, it is often followed by a sharp drop.

Then there are T cells, each specifically tailored to identify a specific pathogen and kill it.Some of these memory T cells can remain in the body for decades until they stumble upon a target, which This means that immunity from vaccines or infections can sometimes last for life But more importantly, you will likely not have many of these cells until the second meeting.

The booster dose is one way to expose the body again to antigens, the pathogenic molecules that stimulate the immune system to initiate the second part of the response. “You have kicked this novelty,” Altmann said, “so when you get the boost, you have a higher frequency of memory T cells, and to some extent increase for the size of the B memory cell group.” Where you have will also generate higher quality antibodies. ”

In a second exposure to the same vaccine or pathogen, B cells that remain from earlier can quickly divide and form a dangerous progenitor, resulting in a second increase in the amount of circulating antibodies.


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