Can vaccines be infected? Can they transmit the coronavirus? DW answers any of the most popular questions about immunizers. As new variants emerge, vaccine effectiveness may be affected

Despite receiving two doses of the vaccine produced by Pfizer-Biotech against covid-19, 14 elderly people from a nursing home in the city of Osnabrück, in northwest Germany, tested positive for the B117 variant of the coronavirus, first discovered in the United Kingdom.

“There have been some cases that are completely asymptomatic and others that are symptomatic, but only with mild conditions,” says Burkhard Riepenhoff, press officer for the municipality of Osnabrück. Testing positive for covid-19 without symptoms or having a mild course of the disease is normal after vaccination – a possible sign that the vaccine is working.

Can vaccines test positive?

Vaccines can create two types of immunity in the vaccinated person: effective immunity or so-called “sterilizing immunity”, which is complete protection against a virus, when no virus particle can enter any cell in the body and cannot replicate, preventing streaming. 

“This is like the Holy Grail of vaccines,” says Sarah Caddy, a viral immunology researcher at the University of Cambridge. “But this is something really difficult to achieve.”

Most vaccines can prevent the virus from causing severe illness, but they do not prevent the person from being infected or transmitting the virus. They manage to limit the amount of virus that enters the body, but there will still be some replication of the virus. “However, vaccination should result in enough antibodies to reduce how much the virus reproduces,” says Caddy. “This is why we are seeing a decline in the disease, but also some replication of the virus, which is then identified as an asymptomatic infection.”

Can vaccinated people transmit the virus?

There is currently insufficient data to know whether covid-19 vaccines, both mRNA and viral vector-based vaccines, can prevent or reduce transmission, according to the Robert Koch Institute (RKI), a German government agency in charge of control. infectious diseases.

Until these data are available, vaccinated people and those around them should continue to follow recommended protective measures, such as wearing a mask, keeping their distance, and washing their hands regularly, warns the RKI.

“Most vaccines cannot stop delivery,” says Caddy, including most vaccines that have been in use for a long time. “They cannot produce sterilizing immunity, but they decrease transmission enough to stop the virus in the population,” he explains.

Can vaccinated people get sick from covid-19 afterward?

It is possible to get sick from covid-19 even after vaccination. But vaccination helps prevent serious illness. Whoever was vaccinated, in case of contagion, is more likely to be asymptomatic or have a mild version of the disease.

The Pfizer-Biotech vaccine is 95% effective in preventing the disease from the original strain, while the Moderna vaccine is 94% effective, and the inoculant from the Oxford-AstraZeneca partnership is 76% effective. 

In tests carried out in many countries, Coronavac, developed by the Chinese Sinovac in partnership with the Butantan Institute, obtained overall effectiveness of 50.38%. The index indicates the vaccine’s ability to protect against all cases of the disease, regardless of severity.

Can the vaccine protect against new variants?

New variants of the coronavirus may influence the effectiveness of current vaccines. Several studies are being carried out in the world with different immunizers to decipher this.

The Pfizer-Biotech vaccine is likely to be effective against the highly infectious variant B117 of the virus, although its effectiveness is slightly affected, according to scientists at the University of Cambridge.

But the E484K mutation – first seen in variant B1351, originally from South Africa – substantially increases the number of antibodies needed to prevent infection. The study has not yet been peer-reviewed and involved only a small number of patients.

The E484K mutation is present both in the coronavirus variant found for the first time in Amazonas, called P1, and in South Africa, also called 501Y.V2.

Another variant found in the United Kingdom has also come to present the E484K mutation in some regions of the country, according to Public Health England, an agency linked to the British Ministry of Health.

South Africa decided to suspend the launch of the Oxford-AstraZeneca vaccine after a study of about 2,000 people found that the vaccine offers little protection against mild and moderate cases of covid-19. The research was carried out by experts from Oxford and Witwatersrand universities in Johannesburg.

Shabir Madhi, a professor of vaccinology at Witwatersrand, told DW that scientific data shows that the Oxford-AstraZeneca vaccine is only 22% effective against the dominant variant in South Africa.

Can the covid-19 vaccine cause a positive test?

Vaccines from Pfizer-Biotech, Moderna and Oxford-AstraZeneca do not give a positive result for covid-19 in viral tests, which are used to check whether the person has an infection at the moment. Vaccines do not contain the coronavirus itself.

When the body of the vaccinated person develops an immune response, which is the goal of vaccination, they may receive a positive result in some antibody tests, which indicate whether the person has previously had an infection, according to the Control and Prevention Center of Diseases (CDC) in the United States.

Can the vaccine against covid-19 cause covid-19?

Pfizer-Biotech, Moderna, and Oxford-AstraZeneca vaccines cannot infect anyone with covid-19 because the vaccines do not contain the coronavirus itself. They teach the immune system to recognize and fight the virus that causes covid-19, according to the CDC. 

Sometimes they can cause symptoms such as fever, headache, fatigue, and muscle aches, which should only last for a few days.

The Corona Vac vaccine, on the other hand, is produced with the coronavirus deactivated and, therefore, cannot cause covid-19 either, as it contains only the virus structure.

What are the most common side effects?

The most common is to feel some redness, heat, and pain in the place where the injection was given. “This is common in virtually all immune responses,” says Caddy. “And the people I know who got the vaccine were very satisfied because it hurt a little bit later, showing that their immune response is working – a slightly sore arm is good; it’s completely normal.”

It may take a few weeks for the body to develop immunity to corona virus after vaccination, according to the CDC. This means that someone can become infected with the virus immediately before or after receiving the vaccine and still develop symptoms of covid-19. But this is only because the vaccine did not have enough time to create protection in the body.

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