Covid 19 coronavirus: Pfizer vaccination provides ‘best immunity’ four weeks after first jab, regulators say

The Pfizer/BioNTech coronavirus vaccination approved in the UK requires four weeks from the first jab for the “best immunity” to be achieved, regulators behind the decision have said.

Meanwhile, those who are first to receive the vaccination will be invited to take part in a voluntary “Yellow Card” monitoring program for side effects.

On Wednesday the UK Medicines and Healthcare products Regulatory Agency (MHRA) became the first in the world to approve a Covid-19 vaccination for widespread use with the first doses to be delivered in days.

Chief Executive Dr June Raine insisted no “corners had been cut” in the approval process and assured the public the decision had been reached following an “extremely thorough and scientifically rigorous review” of the vaccine’s safety, effectiveness and quality.

“The safety of the public will always come first,” she said, adding that the MHRA had completed a “rolling review” to achieve approval in the shortest-time possible.

She described the process as like climbing a mountain which began in June.

“By the time the interim results came in November, we were at base camp,” Raine said, describing the final stretch as a “sprint.”

Australian Health Minister Greg Hunt said Australia could follow suit by March if the Therapeutic Goods Administration approves the jab.

Professor Sir Munir Pirmohamed said immunisation will require two doses 21 days apart.

While “some immunity” is seen 12 days after the first dose, the “best immunity” comes seven days after the second dose, meaning it will be a total of four weeks before people can consider themselves safe from the virus.

Raine thanked those who had enlisted in clinical trials and said they will now be “inviting members of the public to join us in an active monitoring programme” for any potential side-effects.

Monitoring will be based on the existing Yellow Card system in the UK that allows people to report side effects of any drugs or medical devices. The scheme relies on voluntary reporting to flag any early warning signs that may warrant further investigation.

“We still do not know how Covid-19 interacts and behaves with medicines or medical devices used for existing conditions,” the site warns under its Covid page.

“By reporting through this site, patients and healthcare professionals can help gather valuable evidence to inform decisions on the safe and effective use of medicines and medical devices as the pandemic evolves.”

Guidance on the vaccine states that “most side effects are mild or moderate and go away within a few days of appearing”.

Ones dubbed “very common” affecting more than one in 10 people include

• pain at injection site

• tiredness

• headache

• muscle pain

• chills

• joint pain

• fever

Other side affects dubbed “common” affecting up to 1 in 10 include

• injection site swelling

• redness at injection site

• nausea

While “uncommon” ones that may affect up to 1 in 100 people include:

• enlarged lymph nodes

• feeling unwell


The vaccine will be first given to those seen as at most risk of dying from the disease, including elderly, those with pre-existing conditions and frontline healthcare workers before a major public rollout.

That means care home residents will be first, followed by those over 80 and NHS workers, then those over age 75, followed by those over 70 and people with conditions that make them clinically vulnerable, and so on in five-year age brackets.

The next phase will involve general public deployment of the vaccine for those aged 16 and over that will be carried out by local authorities.

However, the vaccine is “not recommended” for children under 16. Women that are pregnant or breastfeeding are also advised there is “limited data” on their situation and to see GP or pharmacist advice.

“As a precaution, you should avoid becoming pregnant until at least two months after the vaccine,” the UK guidance states.

People should let their doctor or pharmacist know if they are taking any other medicines or have recently had any other vaccine.

The rollout will also be complicated by the cold temperatures the vaccine requires to remain stable, of below -70C.

Trials show it remains stable at 2-8C for a short period of time, however the specific cold-storage requirements will send demand for dry ice soaring and could make it particularly difficult to deliver in hot countries in the developing world.


Britain’s Prime Minister Boris Johnson hailed the “fantastic” news that could help the UK get back to normal.

“It’s the protection of vaccines that will ultimately allow us to reclaim our lives and get the economy moving again,” he said.

But Business Minister Alok Sharma was widely panned for a tweet in which he stated: “The UK was the first country to sign a deal with Pfizer/BioNTech – now we will be the first to deploy their vaccine.

“To everyone involved in this breakthrough: thank you.”

“In years to come, we will remember this moment as the day the UK led humanity’s charge against this disease.”

“Wtaf. The vaccine was developed by German scientists in collaboration with a US drug company under the primary auspices of the US FDA. Quit trying to steal other people’s glory,” replied one Twitter user.

“I’m sure the Turkish-Germans who developed the vaccine and the Belgians making it (because the packaging facility was moved from the UK due to Brexit), will be astonished to find they were actually following that great & decisive British leader Johnson,” said another.

“Pfizer is American, BioNTech is German, the vaccine will be made in Belgium. The UK government is proud of “leading the charge” by signing a cheque. Pathetic.”

Meanwhile Interpol has warned of the threat of fake vaccines and stolen supplies as criminal gangs could target those desperate for a virus cure.

“As governments are preparing to roll out vaccines, criminal organisations are planning to infiltrate or disrupt supply chains,” Juergen Stock, head of the global policing agency based in Lyon, France.

“Criminal networks will also be targeting unsuspecting members of the public via fake websites and false cures, which could pose a significant risk to their health, even their lives,” he said.

“It is important to be vigilant, be sceptical and be safe, as offers which appear too good to be true usually are,” the agency said.

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