Physicians have warned against skipping the second dose of the AstraZeneca COVID-19 vaccination.

They noted that such a decision can totally eliminate immunity already built against the virus and increase the risk of vulnerability to variants of COVID-19.

While the first dose might provide some form of protection, the experts said the second dose will further strengthen the immune system due to the high number of antibodies that will be subsequently generated.

According to a preliminary study carried out by scientists at the Oxford University, one dose of the Oxford-AstraZeneca vaccine provides sustained protection against COVID-19 for at least three months and cuts transmission of the virus by two-thirds.

Based on this, the Centres for Disease Control and Prevention insist the second shot is critical in helping to protect people from the virus. 

With Nigeria facing widespread vaccine hesitancy, the country took delivery of its 3.92 million doses of AstraZeneca COVID-19 vaccines from the COVAX facility via the Nnamdi Azikiwe International Airport, Abuja, On March 2.

A few days later, four healthcare workers; Dr. Ngong Cyprian, Nurse Faith E. Eragbai, Dr. Nuru Joseph, and Dr. Thairu Yunusa, were the first to be administered the AstraZeneca vaccine at the National Hospital, Abuja.

This was followed by the President, Major General Muhammadu Buhari (retd.); and Vice President Yemi Osinbajo, receiving theirs at the New Banquet Hall of the Presidential Villa, Abuja.

Following the vaccination and subsequent certification, Buhari became the first among the nation’s strategic leaders to take the vaccine as part of steps to dispel vaccine hesitancy among Nigerians.

Before then, the Executive Director of the National Primary Health Care Development Agency, Dr. Faisal Shuaib, had assured Nigerians of the vaccine’s efficacy, safety, and effectiveness.

On April 20, the NPHCDA revealed that out of the 4.4 million doses of the Oxford-AstraZeneca COVID-19 vaccines received in the country, 1,114, 408 million have been used to vaccinate 55.4 percent of the targeted eligible group.

Meanwhile, the Federal Government had earlier directed state governors not to exceed 50 percent utilisation of the vaccines allocated to their states, to allow for a second dose to those who had taken their first doses.

According to NPHCDA, “As of today, April 20, 1,114,408 representing 55.4 percent of the eligible group targeted with the AstraZeneca vaccine have been administered their first shots in this vaccination phase.

“The 1,114,408, were eligible Nigerians who have been vaccinated from the 36 states and the Federal Capital Territory.”

It revealed that the remaining 50 percent would be administered 8-12 weeks from the date of the first doses. 

Though many people are presently being vaccinated with the Johnson & Johnson, Pfizer-BioNTech, and Moderna COVID-19 vaccines, in various parts of the world, only the AstraZeneca vaccine is being administered in Nigeria.

The second dose of the AstraZeneca vaccine is expected to be given within 8-12 weeks from the date of the initial dose. 

The CDC advised that second shots should be administered, even if there are side effects after the first shot unless a vaccination provider or doctor advises against it.

The Centre also noted that COVID-19 vaccines are not interchangeable, adding, “If you received a Pfizer-BioNTech or Moderna COVID-19 vaccine, you should get the same product for your second shot.”

Speaking exclusively with our correspondent, Head of Haematology and Blood Transfusion at the Lagos University Teaching Hospital, Idi-Araba, Prof. Sulaimon Akanmu, said not taking the second shot of the AstraZeneca vaccine will make the body not generate a sufficient amount of protective antibodies.

He noted that the second dose will protect for 10 to 12 months, while the first, will protect for only three to six months.

“The first dose doesn’t give the maximum level of protection. If the second dose is not taken, the antibody level initially formed will rapidly drop, ”he added.

Akanmu said there are vaccines designed to be administered as a dose, two doses, or booster doses for effectiveness.

He explained that the AstraZeneca vaccine in Nigeria for the Sar-Cov-2 virus is an adenovirus sector-based vaccine, whose mechanism of immunisation differs from that of others.

He said, “With the adenovirus-based vaccine like AstraZeneca, what the manufacturer did was to package the spike protein or the gene that coats the spike protein of the virus inside the adenovirus.

“The adenovirus has been engineered in such a way that the virus is no longer infectious, and is only being used to carry one small gene belonging to the COVID-19 virus. The adenovirus already has an inbuilt mechanism by which, if it gains entrance into the body, it enters into the human cell.

“It has the mechanism by which it introduces its own genetic material to get fitted within genetic material (DNA) of the human cell. This is what the manufactures of AstraZeneca leveraged on.

Continuing, he said, “Indirectly, you now have one small COVID-19 viral gene fitted within the human genome. With this, the gene will become expressed. The gene is copied out as mRNA and it comes out of the nucleus of the cell to the cytoplasm of the cell, and the RNA is able to translate it to the viral protein.

“What we now call the Sars-Cov-2 spike protein is now synthesised by the human cell. The human body has what is called the immune cell (B cell), which will recognise the Sars-Cov-2 spike protein as something new and will begin to mount a humoral immune response (form antibodies).

“So, it is assumed that once you get the COVID-19 vaccine, there is a pre-existing B cell that is going to recognise that particular viral protein. 

That B cell has to undergo clonal expansion – it will divide and go through several stages of maturation until it becomes a plasma cell. It will then, begin to produce a corresponding antibody to the protein that the body has been engineered to produce.

“In the course of maturation of the B cell to become plasma cell, a number of intermediary cells are generated, and only a few of them continue their maturation towards the plasma cell. Those that don’t are referred to as the Memory B cell.”

Akanmu explained that the numbers of B cells that mature to plasma cells are not usually enough to produce a lasting amount of antibody, and there is a need to stimulate or re-stimulate the Memory B Cell, which explains why a second dose of the vaccine is necessary.

“When the second dose is taken and the new proteins come, the Memory B cell will spike them, and when they now begin the maturation stage, they will omit all the maturation stages that they passed through before and begin to produce antibodies in large quantity.

“Some vaccines are designed to work that way and AstraZeneca is one of them. The initial antibody that they generate is usually not long-lasting,” he said.

Speaking also, a Family Physician at the Federal Medical Centre, Makurdi, Benue State, Dr. Laadi Swende, said the elderly and frontline healthcare workers that have received the first shot of the COVID-19 must not skip the second shot to get adequate protection.

“If the shots are not completed as recommended, you are not protected. Taking the first shot doesn’t guarantee that you won’t get infected. If you don’t take it at all, or as recommended, your immunity will be lowered, as against someone who has taken the two doses.

Another Family Physician, Dr. Olawyiwola Bello, said it is imperative to complete the doses.

“If two is the recommended dosage, or three, as is obtainable in some countries, then it has to be completed. Those who have taken the first shot are not likely to experience any side effects with the subsequent one. The doses have to be complete, in order us to have the protection that we desire from the pandemic,” he said.  

 

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