As the UK hits over 18 million doses administered, 1 in 3 adults vaccinated and with orders from five different companies totaling 400 million doses there have been many questions.

How far apart should the doses of vaccines be? What if I miss my second dose? Can I get two doses from two different manufacturers? How was safety of vaccines ensured?

The World Health Organisation (WHO) have tried to answer these questions in there latest Science in 5.

WHO Chief Scientist Dr. Soumya Swaminathan gives a slightly vague answer to the interval question.

She said: “Most of the two those vaccines currently are being given between three to four weeks between the first and the second dose.

“But there is some data from some vaccines like the AstraZeneca vaccine, where delaying the second dose up to 12 weeks actually gives a better immune boost.”

In answering the question relating to the second dose Dr. Swaminathan carried on saying: “It’s important to go back and get that second dose because the first dose actually presents this new antigen to the immune system to prime it.”

The doctor also explained how the two dose system works, saying: “And the second dose is the one that really gives a boost to the immune system so that the antibody response, as well as T cell mediated response, they are very strong and they also develop a memory response, which then lasts for a long time, so that when the body sees this antigen again, this virus protein again, it knows that it needs to react quickly.”

The possibly trickiest question was about the safety of the vaccines saying

“Now, because of the pandemic and the need to get these vaccines out quickly to save lives, the duration of follow up has been a couple of months rather than years, and emergency use authorisations have been given to these vaccines, which means that they are still under observation.”

Though Dr. Swaminathan does finish with the promising point that of the over 150 million doses administered saying: “There hasn’t been anything untoward that’s happened with any of the vaccines that have been really rolled out at a large scale.”

There is a complex question that is asked about mixing vaccines from different companies.

The UK government launched a 13 month study into how a mixed dose vaccination programme could work.

Deputy Chief Medical Officer and Senior Responsible Officer for the study, Professor Jonathan Van-Tam, said: “Given the inevitable challenges of immunising large numbers of the population against COVID-19 and potential global supply constraints, there are definite advantages to having data that could support a more flexible immunisation programme, if needed.

“It is also even possible that by combining vaccines, the immune response could be enhanced giving even higher antibody levels that last longer; unless this is evaluated in a clinical trial we just won’t know.”

It will look at eight different variations that include:

• 2 doses of the Oxford/AstraZeneca vaccine at 28 days apart
• 2 doses of the Oxford/AstraZeneca vaccine at 12 weeks apart – as a control group
• 2 doses of the Pfizer/BioNTech vaccine at 28 days apart
• 2 doses of the Pfizer/BioNTech vaccine at 12 weeks apart – as a control group
• the Oxford/AstraZeneca vaccine for the first dose, followed by the Pfizer/BioNTech vaccine for the second, at 28 days apart
• the Oxford/AstraZeneca vaccine for the first dose, followed by the Pfizer/BioNTech vaccine for the second, at 12 weeks apart
• the Pfizer/BioNTech vaccine for the first dose, followed by the Oxford/AstraZeneca vaccine for the second, at 28 days apart
• the Pfizer/BioNTech vaccine for the first dose, followed by the Oxford/AstraZeneca vaccine for the second, at 12 weeks apart

The advice from the WHO as Dr. Swaminathan states in the video that ‘there isn’t enough data for us to recommend this type of interchangeable two dose schedules’.

Today, Monday February 22, Prime Minister Boris Johnson will be releasing the road map for the exiting of lockdown – which could include the news all UK schools will reopen on March 8.