Pfizer vaccine: When will I become immune to Covid-19?

The vaccine's rollout will be prioritised for those who need it most. Credit: AP

While there is reason to cheer the much-needed arrival of a vaccine approved for use, we are still months away from something resembling normal life returning.

That’s because the UK population cannot simply visit their GP for a jab and be immune in time for the weekend.

Pfizer’s vaccine requires two doses for each person, taken 21 days apart, which means that we will all need a modicum of patience even when we finally get the jab.

Moreover, the UK has ordered 40 million doses – so only around a third of the population will be immunised from Covid-19 with this particular vaccine as it stands.

But the vaccine is highly effective and will safely protect millions in the UK from the pandemic.

Here’s why the vaccine needs a bit of time to give you full immunity from the virus.

Who gets it first?

The vaccine is being rolled out in a targeted way, prioritising those most in need before gradually spreading to other groups.

The Joint Committee on Vaccination and Immunisation (JCVI) has examined data on who suffers the worst outcomes from coronavirus and who is at highest risk of death.

But who will get a jab could depend on how easily one can be rolled out, with the Pfizer jab needing storage temperatures of minus 70C to minus 80C.

For now, the JCVI’s interim guidance says the order of priority should be:

  • Older adults in a care home and care home workers

  • All those who are 80 years of age and over and health and social care workers

  • All those who are 75 years of age and over

  • All those who are 70 years of age and over and clinically extremely vulnerable individuals, excluding pregnant women and those under 18 years of age

  • All those who are 65 years of age and over

  • Adults aged 18 to 65 years in an at-risk group

  • All those aged 60 and over

  • All those aged 55 and over

  • All those aged 50 and over

So when will I become immune?

Nobody can give an exact date for each section of the population as too much relies on the logistical operation running smoothly, which will be a tall order.

Nonetheless, there is a clear timeline for the vaccine’s progress once the first jab is given, as given by Prof Sir Munir Pirmohamed, of the Commission on Human Medicine Expert Working Group.

After the first dose, each person will have only partial immunity – and that’s only after 12 days.

The Pfizer vaccine is more difficult to administer than the Oxford jab Credit: PA Images

But once the second dose is administered – which, remember, must come 21 days after the first – you can expect full immunisation - seven days later.

This means that immunity can be expected 28 days after the first dose.

If the first people were to take their first dose on Tuesday, December 8, then on January 5 the UK will be home to the first people known to have full immunity.

How will it be distributed?

Exactly who will get a jab could depend on how easily one can be rolled out, with the Pfizer jab needing storage at such low temperatures.

There are huge logistical challenges behind delivering a vaccine needing at least minus 70C storage.

Months of preparation has gone into arranging the delivery of a vaccine.

Mass vaccination clinics have been proposed, with a number of venues suggested, including sports halls, leisure centres and even the Copper Box stadium in London’s Olympic Park.

The NHS Nightingale Hospitals have also been earmarked as sites for mass vaccination clinics – among other uses.

The NHS Nightingale Hospitals have also been earmarked as sites for mass vaccination clinics Credit: Stefan Rousseau/PA

Hospitals, GP surgeries and pharmacists have also been put on standby.

Meanwhile St John Ambulance is recruiting thousands of volunteers to help with the rollout.

In addition, NHS leaders have said there will be “roving teams” deployed to vaccinate care home residents and workers.

Pfizer’s manufacturing site in Puurs, Belgium, is being used for European supply.

The vaccine will be delivered by plane – Pfizer has already ruled out ocean transport due to timings.

The company has created special suit-cased size containers fitted with temperature and GPS trackers to ship the vaccine.

Once the vaccine supply arrives in the UK it will undergo quality checks to ensure it has been shipped safely.

The vaccine will then be unloaded and moved to storage freezers where it will undergo a further temperature check. How does the vaccine actually work?

Pfizer's vaccine is an mRNA vaccine. Credit: PA

The jab is known as a messenger RNA (mRNA) vaccine.

Conventional vaccines are produced using weakened forms of the virus, but mRNAs use only the virus’s genetic code.

An mRNA vaccine is injected into the body where it enters cells and tells them to create antigens.

These antigens are recognised by the immune system and prepare it to fight coronavirus.

No actual virus is needed to create an mRNA vaccine. This means the rate at which it can be produced is dramatically accelerated.

As a result, mRNA vaccines have been hailed as potentially offering a rapid solution to new outbreaks of infectious diseases.

In theory, they can also be modified reasonably quickly if, for example, a virus develops mutations and begins to change.

mRNA vaccines are also cheaper to produce than traditional vaccines, although both will play an important role in tackling Covid-19.

One downside to mRNA vaccines is that they need to be stored at ultra-cold temperatures and cannot be transported easily.