The EU’s medicines regulator has just approved a third COVID-19 vaccine for use across the bloc, as countries continue to struggle to get the virus under control. But taking the jab is not a licence for ‘normal’ behaviour. Giulia Magri answers some important questions about vaccination.

How long does it take for the vaccine to start working?

It takes a week or two for immunity to develop following vaccination, depending on what type of vaccine is taken.

According to the US Centers for Disease Control and Prevention (CDC), the Moderna vaccine is 94.1 per cent effective in protecting against COVID-19 in people who have received two doses. Studies show this efficacy is reached 14 days after the second dose.

According to data from a second vaccine manufacturer, published last month, the Pfizer-BioNTech vaccine is roughly 52 per cent effective after the first dose and 95 per cent after the second. Protection does not start developing until at least 12 days after the first dose is taken. 

The third vaccine, from AstraZeneca, has shown a 60 per cent efficacy from clinical trials, according to the European Medicines Authority. The company says effectiveness at preventing symptoms of COVID-19 is achieved more than 14 days after receiving both doses. 

How long will immunity last after being vaccinated?

Both the EMA and CDC say there is not enough data yet on how long protection lasts.

Some researchers also claim that a booster shot may be required after a few years. The possibility of a booster shot is also being looked at in relation to the new variants.

Researchers are looking into the differences between natural immunity and vaccine-induced immunity.

Can vaccines protect against mutations of the virus?

Studies have shown that the vaccines appear to work well against the variants found in the UK and South Africa, although research here is ongoing.

AstraZeneca has said its scientists are "carefully assessing the impact of new variants" and preparing to adjust the company's COVID-19 vaccine if needed. 

Pfizer and Moderna have both said they are working to develop a third dose to their vaccine regime, to serve as a booster shot to protect against variants. 

It is important to note that all viruses mutate over time, and the SARS-CoV-2 virus is no different. Other, as-yet-unknown variants may yet develop. 

What happens if I test positive for COVID after taking the first dose?

Coronavirus vaccines cannot infect anyone with COVID-19 since they do not contain the virus.

There have been cases of people testing positive after getting the first vaccine dose. This does not mean the vaccine has failed to work but that the person was probably exposed to COVID-19 before getting the jab.

If this happens, they must wait four weeks before taking the second dose, enough time to have recovered and be out of quarantine.

Since there is still a chance of transmission, vaccinated persons are not exempt from quarantine, especially if they have been in close contact with someone who has tested positive.

Can I still transmit the virus after vaccination?

We still do not know. While early studies have shown that vaccinated people are far less likely to become seriously ill with coronavirus, it is not certain yet whether it stops them from actually getting infected and passing the virus on to others.

In any case, the vaccines are not 100 per cent effective and it takes time for them to provide the protection they do.

The EMA says it is not yet known to what extent vaccinated people may still be able to carry and spread the virus and the CDC recommends that vaccinated people do not make the assumption they are completely immune to infection.

Do I still need to follow the social distancing guidelines if I get vaccinated?

Yes. You may be immune to the virus but still be capable of transmitting it to others. There is simply not yet enough information to recommend that vaccinated people stop following COVID-19 protocols.

Both the CDC and EMA say people should abide by all restrictions for now: social distancing, wearing a face mask, avoiding crowds, limiting the size of gatherings and practising good hygiene.

Health authorities have said that such measures will still be needed for several more months until a high percentage of the population is vaccinated and herd immunity starts to be achieved.

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