Covid-19 vaccine safety: We speak to Pfizer's medical director in SA – Part 1

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  • Covid-19 vaccines are a critical part of addressing the pandemic, as they can reduce infection and death worldwide. 
  • One of the vaccines developed and being rolled out is the two-dose Pfizer-BioNTech vaccine.
  • Dr Bha Ndungane-Tlakula, Country Medical Director at Pfizer South Africa, answers key questions about the vaccine.

The development and rollout of vaccines are critical in our fight against the Covid-19 pandemic. While the vaccines are the quickest to have been developed in history, it doesn't mean the process skipped any critical steps.

In a two-part series, Health24 chatted to Dr Bha Ndungane-Tlakula, Country Medical Director at Pfizer South Africa, about the Covid-19 Pfizer vaccine which is currently being administered in South Africa and more than 100 other countries all over the world. 

1. The Pfizer vaccine uses novel vaccine technology and was developed very quickly – how do we know it is safe?

It took less than a year to develop the Covid-19 vaccines. The fastest any vaccine had ever been developed, prior to this pandemic, was four years for mumps in the 1960s, notes an article by Nature. Since the Covid vaccines were developed at a much faster pace, it has generated some concern around its safety and effectiveness among the general public. Ndungane-Tlakula explained how Pfizer and BioNTech went about the process:

"We knew early on that a safe and effective vaccine would be essential to ending the pandemic. So, we combined our industry-leading vaccine development, manufacturing and distribution capabilities with BioNTech’s expertise in innovative mRNA technologies to quickly develop, manufacture and distribute large quantities of high-quality Covid-19 vaccine. 

"Given the urgency of the situation, Pfizer self-funded more than $2 billion at risk to run clinical development and manufacturing processes in parallel and at scale. Collaborating closely with regulatory and health authorities around the world, including the EMA here in Europe, we compressed timelines that typically take years into months, and those that take months into weeks." 

Patients and science were at the forefront of the company's efforts, he said, and reassured that no shortcuts were taken. Instead, Pfizer "rather worked innovatively to conduct key steps of the process in parallel rather than the usual sequential approach." 

Ndungane-Tlakula added: "As a result, we were able to move at the speed of science and make the seemingly impossible possible: delivering in less than a year a breakthrough Covid-19 vaccine that has received authorisation and recommendation in Europe and with authorities globally." 

2. How does the Pfizer vaccine work?

The Pfizer vaccine is one of two Covid vaccines (the other being Moderna's jab) that uses messenger RNA technology (mRNA), which teaches our cells how to make a protein that triggers an immune response. Ndungane-Tlakula explained:

"The BNT162 mRNA vaccine works by conveying genetic instructions to cells to make spike protein antigens specific for the virus. The antigens will then be recognised by the immune system of the vaccinated individual, generating an antibody response to inactivate (neutralise) the SARS-CoV-2 virus." 

3. Why does the Pfizer vaccine require two doses, compared to other single-dose vaccines?

"Although partial protection from the vaccine appears to begin as early as 12 days after the first dose, two doses of the vaccine are required to provide the maximum protection – a vaccine efficacy of 95% – observed in the Phase 3 trial," said Ndungane-Tlakula.

4. Does the vaccine protect against the new variants of concern?

Covid vaccine developers have had to continuously update and test their shots to provide protection against the new variants of the SARS-CoV-2 virus, including the Beta (first identified in South Africa) and Delta (first identified in India) variants.

Ndungane-Tlakula said that, to date, Pfizer is encouraged by the real-world data and laboratory studies of their vaccine and that there is no evidence that the virus or circulating variants of concern (VOC) regularly escape immune protection.

"We are monitoring trial participants from our landmark Covid-19 vaccine study for two years after their second dose to learn more about the vaccine’s protection against this disease, and to be as prepared as possible, we are also studying a booster dose and prototype vaccine with a variant sequence for use against new strains that may emerge," he said, adding:

"Recently, Nature published a paper on a lab study of the neutralising activity of Pfizer-elicited serum against SARS-CoV-2 variants of concern. The results suggested neutralisation of all variants, including the Delta variant, except that neutralisation of Delta was efficient but modestly reduced relative to previous strains."

Similarly, he said, a study by Public Health England in the UK found that the real-world effectiveness of two doses of the Pfizer vaccine against the Delta variant was only modestly reduced to 87.9%, compared to 93.4% effectiveness against the Alpha variant.

"The neutralisation data provide strong support that the Pfizer vaccine will continue to protect against these variants. We will continue to monitor the effectiveness of our Covid-19 vaccine as variants become known to us," said Ndungane-Tlakula. 

5. Once the jab is given, when does protection against Covid-19 start?

The Pfizer vaccine provides partial protection against Covid-19 after the first dose, and this can begin as early as 12 days after vaccination, but Ndungane-Tlakula stressed that two doses of the vaccine are required to provide the maximum protection.

6. How long does vaccine-induced protection last?

There are some uncertainties regarding immunity after vaccination, including how long it lasts, but this is something Pfizer continues to explore. Said Ndungane-Tlakula: "Recently, Pfizer and BioNTech shared a topline safety and efficacy update from our landmark Phase 3 global study with efficacy measured from seven days to six months after the second dose.

"We continue to monitor participants vaccinated for a full period of two years, and at this time, more than 50% of participants have reached at least the six-month mark." 

7. Should I expect any unforeseen future, long-term, negative effects?

During the Phase 3 trial, some participants reported mild to moderate injection site pain within seven days after injection, said Ndungane-Tlakula, but that, generally, local reactions were mostly mild to moderate in severity. These side effects also resolved within one to two days. 

He added: "We will continue to monitor participants for two years following their second dose of the Covid-19 vaccine."

8. Will I need a booster shot?

Experts have been weighing the need for Covid booster shots to bolster immunity against the disease. 

According to Ndungane-Tlakula, while neutralising antibodies (which blocks the virus from infecting human cells) have been decreasing in vaccine recipients over a six-month period, Pfizer's analysis shows that their vaccine continues to be highly effective against the disease through six months. The company will continue to study vaccine efficacy and safety moving forward. 

"However, to address any potential future reduction in the persistence of protection after six months, we have already implemented a study as part of our broad vaccine development plan to evaluate a third dose of our Covid-19 vaccine," said Ndungane-Tlakula.

Testing the safety and immunogenicity (a measure of how well a vaccine works) of a third dose of the Pfizer vaccine will allow scientists to understand the effect of a booster on immunity against Covid caused by the circulating and potential newly emerging variants, he added.

"Based on what we have learned so far, our current thinking is that until we see a reduction in SARS-CoV-2 circulation and Covid-19 disease, we think it is likely that a third dose, a boost of our vaccine, within 12 months after vaccine administration, will likely be needed to help provide protection against Covid-19, subject to approval by regulatory authorities, explained Ndungane-Tlakula.

The company is also prepared to update their vaccine quickly should new variants emerge and is shown to escape current vaccine protection, he added.

*For more Covid-19 research, science and news, click here. You can also sign up for our Daily Dose newsletter here.

READ | Delta variant in SA: Why getting your second shot of the Pfizer vaccine is so important

READ | Covid-19 vaccines and the Delta variant: What we know

READ | Sahpra’s Covid-19 vaccine approval process: ‘The safety of the public takes precedence’

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