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How long does it take for corona vaccines to start working?

Clinical trials show that protection from the Corona vaccine is optimal two weeks after receiving the second dose, and this means that it fully protects against severe illness and death in healthy people, and also significantly reduces the possibility of symptoms of COVID-19.

Theconversation website report stated that in the event of infection, the vaccine reduces the amount of the virus, and evidence indicates that this reduces the possibility of transmitting the virus to other people.

How about a single dose of Pfizer?

Clinical trials of the Pfizer vaccine are designed to test the vaccine's efficacy more than a week after the second dose, yet these trials also provided the first indications that a single dose could provide some protection as early as 12 days afterward.

The report said that a single dose of the Pfizer vaccine is very effective to prevent the need for hospitalization four weeks after vaccination, and it is effective between 50% and 90% in preventing infection.

What about a single dose of AstraZeneca?

AstraZeneca was initially developed as a single-dose vaccine and is estimated to have a 76 percent efficacy against the disease in clinical trials. Those trials were later modified to include a second dose, when further work showed that two doses significantly increased antibody levels in volunteers.

The data, not reviewed, showed that a single dose of AstraZeneca was 65% effective in protecting against infection, and 50% effective in reducing transmission of the virus if they became infected.

What is taking so long?

Despite the differences in mRNA vaccines such as Pfizer and virus vector vaccines such as AstraZeneca, both take a similar time to generate antibody responses. After one dose of AstraZeneca, antibodies can be detected after 14 days and another increase over the next two weeks.

But why does it take time for these responses to appear? When researchers tracked the antibody response to the first dose of the vaccine, they found that it takes at least ten days for the immune system to start making antibodies that can recognize the coronavirus (a protein on the surface of the virus that it uses to enter the body's cells).

It also takes at least a week for T cells, a type of white blood cell important in our immune response, to kick in, while the second dose activates the immune system more quickly.

Within a week of the second dose, your antibody levels increase by more than ten times, providing stronger and longer-lasting protection from infection.

So the first dose of the COVID vaccine increases the immune response, but the second dose is necessary to ensure that immunity is strong, consistent from person to person, and long-lasting.