To be approved for emergency use, a vaccine has to demonstrate itself to be safe and effective during clinical trials, explained UWI professor of Molecular Genetics and Virology, Christine Carrington.

For full approval, clinical trials have to show the vaccine is safe, that it works and it has to be known how long the protection would last. Any adverse effects would have likely happened in the first two to three months after vaccination and would have been seen in the trials.

So even though several vaccines were only given Emergency Use Approval by the World Health Organization, it is still safe to use.

Speaking at the Ministry of Health virtual press conference on Saturday, Carrington said, 'We don't have time to wait two years to find out if the vaccine is going to protect us for two years. It's an emergency. So nobody knows at this stage how long it (immunity) will last.

'It's important to remember that your immune system, although you lose some of those antibodies, your body remembers how to make them and how to make them quickly so should you get infected again, that disease is expected to be mild.'

She said both natural and vaccine immunity seemed to start declining around six to nine months. Not enough time had passed to be sure any vaccine could give lifetime protection.

Addressing herd immunity with the covid19 vaccines, Carrington stressed that being infected was different from being sick. The aim of the vaccines was to keep people as healthy as possible.

'Yes, vaccinated people can become infected and can transmit the virus to others but the rate at which they do so is much lower than for unvaccinated people.

'And when you're talking about herd immunity you're talking about a population level of protection so although there is variation in the individual level, once you reduce the risk of individuals transmitting, the overall effect on the population is more protection across the entire population.'

She said if the virus was not controlled through vaccination and would be allowed to spread among the population, resulting in a bigger chance of worst variants arising.

Asked why the public health restrictions limiting people's movement did not seem to be making significant improvements in the number of new cases, she said it would be a slow process.

She reminded that infection was an exponential growth where one could infect several and each of them in turn could infect several others. In addition, TT was coming down from a high peak and there was still interaction between people, so there would be more cases.

'So when you try to counter that it's not a simple linear equation bringing you down from a peak. You are battling an uphill trend so it takes some time. It will take more time.'

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