- Covid-19 vaccines are a critical part of addressing the pandemic, as they can reduce rates of 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 education 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 over 100 other countries all over the world.
(Find part 1 here.)
1. Can I get Covid disease after receiving the vaccine?
In some cases, people who are fully vaccinated may still become infected with Covid-19. These are known as "breakthrough infections". However, symptoms in these cases are likely to be mild or asymptomatic (displaying no symptoms), according to the US Center for Disease Control and Prevention (CDC).
Ndungane-Tlakula said that this is an area that Pfizer is continuing to research. "We are testing a subset of Phase 3 trial participants for antibodies against the N protein and comparing results at baseline (before immunisation) and at various intervals after immunisation to look for evidence of infection, whether symptomatic or not," he said.
The Pfizer clinical trial protocol has also been amended, Ndungane-Tlakula added, so that some investigator sites may collect information to help the companies evaluate the effectiveness of the Pfizer vaccine in preventing Covid infections or asymptomatic transmission.
"Understanding whether the vaccine can stop the transmission of the virus will be an important tool for the continued rollout of the vaccine and to inform public health planning efforts and recommendations," said Ndungane-Tlakula.
According to Ndungane-Tlakula, already enrolled trial participants in the US who decide to participate in this part of the study have the option to self-administer a nose-swab every two weeks and drop off the supplied kit at a UPS store or study site, or come to the study site every two weeks to have the nose swab performed by study staff.
"Additionally, we have seen in real-world studies that there is evidence that the vaccine prevents asymptomatic infection," he added.
2. If I had Covid-19 and recovered, should I still get both doses of the vaccine?
Ndungane-Tlakula advised that recommendations on dosing regimens should reside with health authorities and may include recommendations due to public health principles.
"As a biopharmaceutical company working in a highly regulated industry, our position is supported by the label and indication agreed upon with regulators and informed by data from our Phase 3 study. Pfizer and BioNTech’s Phase 3 study for the Covid-19 vaccine was designed to evaluate the vaccine’s safety and efficacy following a two-dose schedule, separated by 21 days," he said.
Guidance by the World Health Organization (WHO) states that people who have already had Covid infection should still get vaccinated, unless told otherwise by their healthcare provider.
"Even if you’ve had a previous infection, the vaccine acts as a booster that strengthens the immune response. There have also been some instances of people infected with SARS-CoV-2 a second time, which makes getting vaccinated even more important," says the health agency.
On whether people with previous Covid infection should receive both doses, some countries, including France, Germany, and Italy are advising only one dose of vaccine for those with a healthy immune system and a confirmed previous diagnosis. But scientists have also stressed that some people who become infected with the virus mount a relatively weak immune response, which means both doses may be needed after all, reports Nature.
3. Is it safe for people with underlying medical conditions or weakened immune systems?
Pfizer's Phase 2/3 clinical trial included people with comorbidities. The most frequently reported comorbidities were obesity (35.1%), diabetes (with and without chronic complications, 8.4%) and pulmonary disease (7.8%), explained Ndungane-Tlakula.
A recently updated real-world study showed that this vaccine was "exceedingly effective" among high-risk groups, including in overweight and obese patients, immunosuppressed individuals, and patients with heart disease and diabetes, among others, Health24 reported.
4. Has the vaccine been tested in pregnant women?
"The Phase 2/3 clinical trial to evaluate the safety and immune response in healthy pregnant women 18 years or older between 24 and 34 weeks of pregnancy commenced in February 2021. We plan to enroll approximately 4 000 participants at more than 130 global sites," said Ndungane-Tlakula.
Each participant, he said, will participate in the study for approximately seven to 10 months, depending on whether they were randomised to receive the vaccine or placebo. Initial data from this study is expected later in 2021.
5. Can the vaccine cause infertility as a side effect?
The CDC notes that there is currently no evidence that any of the Covid-19 vaccines cause female or male fertility problems.
"Pfizer’s vaccine candidate has not been found to cause infertility," confirmed Ndungane-Tlakula. "It has been incorrectly suggested that Covid-19 vaccines will cause infertility because of a shared amino acid sequence in the spike protein of SARS-CoV-2 and a placental protein."
He added: "The sequence, however, is too short to plausibly give rise to autoimmunity. Additionally, a cohort study comparing the outcomes of pregnancies with and without intercurrent SARS-CoV-2 infection shows no difference in outcomes, further debunking the theory."
6. Is there anyone who should not get the Pfizer vaccine?
The US Centers for Disease Control and Prevention advises that you should not get the Pfizer vaccine if you have had a severe allergic reaction, known as anaphylaxis, or an immediate allergic reaction – even if it was not severe – to any ingredient in the vaccine.
Additionally, it states, you should not get the vaccine if you had a severe or immediate allergic reaction after getting the first dose of the vaccine.
7. Can an mRNA vaccine alter my DNA or case gene editing?
MRNA vaccines don't carry these enzymes, explains GAVI (the Vaccine Alliance), which means there isn't any risk of the genetic material they contain altering a peron's DNA.
Ndungane-Tlakula weighed in: "Rather than a traditional vaccine that uses 'inactivated' or dead virus, or portions of the virus to spur an immune response, mRNA delivers a message to your body’s cells (via a lipid nanoparticle envelope) that instructs the cells to generate the spike protein (the part of the virus that enables entry into human cells).
"This is a protein on the surface of a coronavirus that initiates the infection in human cells. Instructing cells to generate the spike protein spurs an immune response, including generating antibodies that are specific to the Covid spike protein.
"It is widely believed that RNA (or ribonucleic acid) is unable to integrate into the human genome, which is comprised of deoxyribonucleic acid. Hence, we believe that the mod RNA in mRNA vaccines are unable to integrate into the human genome."
8. Does the vaccine contain any components of animal origin or cell lines from aborted foetuses?
Since the Pfizer vaccine consists of synthetic and enzymatically produced components, it contains no animal products, said Ndungane-Tlakula.
"Human foetal derived cell lines are also not used to produce our vaccine but some (but not all) confirmatory laboratory tests associated with the vaccine programme used HEK293 (human embryonic kidney) cells," he added.