Understanding the Pfizer/BioNTech COVID-19 Vaccine

What are vaccines and how do they work?

Vaccines contain either weakened or inactive parts of an antigen that, when injected or ingested into our body, stimulate our immune system to produce antibodies against the antigen. These ‘antigen parts’ do not cause disease in themselves. Rather, they mimic infection and, in doing so, provide our immune system with enough information for it to create the antibodies needed to prevent disease if we are ever exposed to the antigen in the future.1,2

As vaccines are about protecting the health of individuals and communities, they ideally need to be able to do several things:

  1. prevent us from becoming infected with a disease;
  2. prevent serious illness if we do become infected with a disease;
  3. reduce the mortality rate caused by a disease;
  4. in a pandemic, ease the strain on healthcare workers and healthcare systems by reducing the number of people becoming severely ill from a disease;
  5. in a pandemic, reduce the ‘knock on’ mortality rate from other illnesses due to the overloading of the healthcare system because of a disease;
  6. prevent symptomatic and asymptomatic transmission of a disease from those who have it to those who do not have it;
  7. provide ongoing immunity for the future.

What is an mRNA vaccine and how does it work?

‘mRNA’ stands for ‘messenger ribonucleic acid’. mRNA is a molecule that occurs naturally in the body. It is involved in protein synthesis – the process via which our body produces all the different proteins we need to live, including antibodies. An mRNA vaccine, such as the Pfizer/BioNTech COVID-19 vaccine, harnesses this process. The vaccine contains an mRNA molecule that carries the specific instructions for how to make the SARS-CoV-2 ‘spike’ protein – the non-disease-causing prickly projection on the surface of the COVID-19 virus that is characteristic of it and unique to it. Once injected into the body, the mRNA molecule is taken up into our cells where it instructs the cells to make this spike protein. When our cells have finished making this spike protein, our body recognises it as a foreign antigen (a germ), with our immune system responding by creating an antibody against it. This means that if we are ever infected with the COVID-19 virus in the future, our body will recognise the virus and produce antibodies to protect us from it. Once the mRNA in the vaccine has fulfilled its function, naturally occurring enzymes in the body degrade the mRNA and our body disposes of the debris.3,4

Does the mRNA in the Pfizer/BioNTech vaccine affect DNA?

No, the mRNA in the vaccine does not affect DNA for two reasons:

(i)    mRNA cannot enter the nucleus of our cells, the place where our DNA (genetic material) is housed;
(ii)    the cell breaks down and destroys the mRNA soon after it is finished using the instructions.5

Is the Pfizer/BioNTech vaccine safe?

As with all medicines and medical treatments, vaccines are not 100% completely risk-free.6 Nevertheless, evidence from decades of research and monitoring indicates that, on the whole, vaccinating against a given disease is much safer than not vaccinating, and that the vast majority of people can safely be given vaccines.7 

In terms of the Pfizer/BioNTech vaccine, the US Centers for Disease Control and Prevention continues to monitor the safety and efficacy of all COVID-19 Vaccines.8 In New Zealand, Medsafe and the COVID-19 Vaccine Independent Safety Monitoring Board also have a monitoring role. As noted by New Zealand Doctor, the COVID-19 Independent Safety Monitoring Board “is independent of the COVID-19 immunisation programme, Medsafe and Ministry of Health” (see https://www.nzdoctor.co.nz/article/undoctored/covid-19-independent-safety-monitoring-board). Severe reactions remain, relatively speaking, rare.

As of the 31st of January 2023, a total of 11,976,900 doses (cumulative) of COVID-19 vaccines had been administered in New Zealand (see https://www.health.govt.nz/covid-19-novel-coronavirus/covid-19-data-and-statistics/covid-19-vaccine-data). As of the 30th of November 2022, Medsafe reports there were a total of 3,688 reports of a serious side effect (see https://www.medsafe.govt.nz/COVID-19/safety-report-46.asp).

As of 14 December 2022, the COVID-19 Vaccine Independent Safety Monitoring Board has notified Te Whatu Ora of four deaths in New Zealand in which a link to the Pfizer/BioNTech COVID-19 vaccine could not be excluded.9

Myocarditis (see https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/is-the-covid19-vaccine-safe) is a documented and serious, rare side-effect of the Pfizer mRNA vaccine. The full range of various side effects, reported adverse events and allergic reactions to the Pfizer and Novavax vaccines are listed on the New Zealand Ministry of Health website: https://www.health.govt.nz/covid-19-novel-coronavirus/covid-19-vaccines/covid-19-vaccine-side-effects-and-reactions#:~:text=Myocarditis%20and%20pericarditis,-Myocarditis%20is%20inflammation&text=Symptoms%20of%20myocarditis%20or%20pericarditis,should%20seek%20prompt%20medical%20help.

Part of the New Zealand Medsafe “review process includes comparing natural death rates to observed death rates following vaccination, to determine if there are any specific trends or patterns that might indicate a vaccine safety concern.” The Medsafe Safety Report #46 (30 November 2022) notes: “To date, the observed number of deaths reported after vaccination is actually less than the expected number of natural deaths.”10

As of 7 February, 2023, it is calculated that there have been a total of 2,502 deaths directly attributed to COVID-19 in New Zealand (see https://www.health.govt.nz/covid-19-novel-coronavirus/covid-19-data-and-statistics/covid-19-current-cases)

How effective is the Pfizer/BioNTech vaccine?

While it was initially hoped that people who were vaccinated would be protected from being infected, it is now well-established that ‘vaccine breakthrough infections’ do occur. As of 30 January 2023, the total number of active cases since the first New Zealand case stands at 2,182,355 (see https://www.health.govt.nz/covid-19-novel-coronavirus/covid-19-data-and-statistics/covid-19-current-cases)

Excluding those under 12 years of age, of the total number of active cases of COVID-19, 96,249 cases had either no doses of vaccine (78,000) or were only partially vaccinated (18,249). This means that unvaccinated persons make up 5% of all cases. Conversely, it means that 95% of all active cases of COVID-19 occurred in fully vaccinated people (defined as those with or without boosters).

The benefits of vaccines, however, are better measured by the rates of serious illness and hospitalisations for COVID-19 cases. The 5% of those with no doses of vaccine or only partially vaccinated make up 14.8% of hospitalisations for COVID-19. This means that unvaccinated/partially vaccinated people are 3.3 times more likely to be hospitalised when compared to "fully vaccinated" people (defined as those with or without boosters): Note: numbers used are rounded to two significant figures.

In addition, the 5% of those with no doses of vaccine or only partially vaccinated make up 23.6% of all ICU care admissions. This means that unvaccinated/partially vaccinated people are 5.9 times more likely to be admitted to ICU than "fully vaccinated" people (See https://www.health.govt.nz/covid-19-novel-coronavirus/covid-19-data-and-statistics/covid-19-case-demographics)

Vaccine effectiveness is typically measured through observational studies specifically designed to estimate individual protection from vaccination under “real-world” conditions.11 Numerous research projects have verified that vaccine effectiveness against moderate and severe COVID-19 wanes with time after vaccination.12

Meanwhile, research published in the medical journal Lancet in November 2022 shows, encouragingly, that the natural immunity which arises from contracting COVID-19 (regardless of the variant) is superior to that generated by the mRNA vaccinations alone (see https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(22)00287-7/fulltext#seccestitle150). At the same time, the authors of this study conclude that “Vaccination remains the safest and most optimal tool for protecting against infection and COVID-19-related hospitalisation and death, irrespective of previous infection status.” This is because “Natural infection can lead to COVID-19-related hospitalisation and death at the time of primary infection, and long COVID-19 after the infection, which are risks not present with vaccination” – i.e., whilst research at this stage suggests that natural immunity is stronger, it comes at a significantly higher risk of becoming seriously ill from the initial infection than those who are vaccinated. The authors further note: “The rapid waning of protection of primary-series vaccination supports the need for scaling up of booster vaccination and development of more potent vaccines to mitigate the effect of emerging variants.”

The Centres for Disease Control and Prevention (updated November 10, 2022) similarly notes: Being up to date on COVID-19 vaccines continues to provide strong protection against severe disease, hospitalization, and death in adults and children, including during Omicron variant predominance. Effectiveness against infection has waned across all age groups, but this is expected.”13

What about Long COVID?

The National Institutes of Health define Long COVID as follows: “Long COVID, long-haul COVID, post-COVID-19 condition, chronic COVID, and post-acute sequelae of SARS-CoV-2 (PASC) are all names for the health problems that some people experience within a few months of a COVID-19 diagnosis. Symptoms of Long COVID may be the same or different than symptoms of COVID-19. Long COVID can also trigger other health conditions, such as diabetes or kidney disease (see https://covid19.nih.gov/covid-19-topics/long-covid#:~:text=Long%20COVID%2C%20long%2Dhaul%20COVID,of%20a%20COVID%2D19%20diagnosis. – page updated 5 October 2022 and last accessed 9 February 2023). In an earlier article, dated May 16, 2022, the National Institutes of Health note: “Long COVID is marked by wide-ranging symptoms, including shortness of breath, fatigue, fever, headaches, ‘brain fog’ and other neurological problems. Such symptoms can last for many months or longer after an initial COVID-19 diagnosis. One reason long COVID is difficult to identify is that many of its symptoms are similar to those of other diseases and conditions” (see https://www.nih.gov/news-events/news-releases/scientists-identify-characteristics-better-define-long-covid - last accessed 9 February 2023).

It is estimated, conservatively, that the incidence of long COVID is around 10%, the actual number likely to be much higher due to many undocumented cases. (See Davis, H. et al. (2023) Long COVID: major findings, mechanisms and recommendation: https://www.nature.com/articles/s41579-022-00846-2 - last accessed February 2023). The authors of this review article report: “The incidence is estimated at 10–30% of non-hospitalized cases, 50–70% of hospitalized cases and 10–12% of vaccinated cases.” In a related study, Ayoubkhani et al (2022) conclude that “COVID-19 vaccination is associated with reduced risk of Long Covid, emphasising the need for public health initiatives to increase population-level vaccine uptake (see https://www.medrxiv.org/content/10.1101/2022.02.23.22271388v1 – last accessed February 2023.

What is the current evidence for receiving further COVID-19 vaccine boosters?

While the mRNA vaccination programme has been demonstrated to be less effective in preventing transmission of the COVID-19 virus and mild disease, various overseas studies show that the use of a bivalent booster is effective in preventing severe disease (see Professor Nikki Turner, Director Director, Immunisation Advisory Centre, University of Auckland, quoted 19 January 2023 in ‘Does NZ need a bivalent booster? – Expert reaction at https://www.sciencemediacentre.co.nz/2023/01/19/does-nz-need-a-bivalent-booster-expert-reaction/ (last accessed 9 February 2023). The effectiveness of using a bivalent booster vaccine (which contain mRNA-encoding proteins from both the original 2020 strain of the virus and an Omicron variant – either BA.1 or BA.4/5) has been demonstrated by clear differences between the unvaccinated, those vaccinated but without boosters and those who have received the bivalent booster. Thus Professor Turner further notes: “A [preliminary] Israel study including 700,000 participants showed 81% reduction in hospitalisations and 86% reduction of deaths using the bivalent in adults 65 years and older (see https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4314067&utm_source=substack&utm_medium=email – last accessed 9 February, 2023).

Similarly, a Centers for Disease Control and Prevention (CDC) Report published in January 2023 concludes: “In November 2022, compared to adults ages 18 years and older who received an updated COVID-19 bivalent booster dose, monthly rates of COVID-19-associated hospitalizations were 16.0x Higher in Unvaccinated and 2.7x Higher in Vaccinated Adults without an updated booster. Broken down by age groups, this study showed that hospitalisation rates were 29.9x higher for unvaccinated adults aged 18-49 years and 3.2x higher for those in the same age group who were vaccinated but without an updated booster (see https://www.cdc.gov/coronavirus/2019-ncov/covid-data/covid-net/hospitalizations-by-vaccination-status-report.pdf – last accessed 9 February 2023).

As of February 2023, the bivalent booster has not been made available in New Zealand.

Has anyone caught COVID-19 from having the Pfizer/BioNTech vaccine?

No. It is not possible to catch COVID-19 from the vaccine because the vaccine does not contain any live virus – it is an inert, lifeless vaccine.14

I have heard that there is a historical link between abortion and the vaccine. Is this true? What is the relationship between the Pfizer/BioNTech vaccine and human foetal cells/ tissue?

There is a distant, historical link between abortion and the Pfizer/BioNTech vaccine.15 Some of the COVID-19 vaccines that have been developed rely on human cell lines (started with cells that originally came from an electively aborted foetus) for their production.16 

While the Pfizer/BioNTech vaccine does not require the use of such cell lines for its production, it has been tested using an ethically compromised human cell line, HEK293.17 In the case of the development of the Pfizer/ BioNTech vaccine, the HEK293 cells used in the testing phase trace their ancestry back to a foetus legally aborted in the Netherlands in the 1970s for reasons unrelated to medical research. The cells used for testing are not the original cells taken from the foetus itself but are descendants of those cells. These descendent cells are referred to in biomedical research as ‘immortal cell lines’ because they are artificially maintained in a state of continual replication under laboratory conditions. No new foetal tissue is needed to maintain the cell line.

Therefore, the cell line in question, HEK293, does not require further abortions for its continued existence.18 This fulfils an important moral criterion for establishing moral justification in situations where a well-intentioned action has unavoidable negative consequences; the chosen action (being vaccinated) will not lead to further immoral outcomes (additional abortions).19

Must Catholics reject the Pfizer/BioNTech vaccine on religious grounds?

No. In the context of the COVID-19 pandemic, being vaccinated can be accurately described as an act of solidarity that upholds our duty to the common good and that protects those who are most vulnerable amongst us.20 In a note on vaccines published in 2017, the Pontifical Academy for Life has stated that “the wrong in the moral sense lies in the actions [of those involved in the original abortion] not in the vaccines or the material itself.” See (https://www.academyforlife.va/content/pav/en/the-academy/activity-academy/note-vaccini.html accessed January 2023) This means that the use of such vaccines does not, in itself, signify moral endorsement of the vaccine production process or complicity with abortion.21 The Vatican’s Congregation for the Doctrine of the Faith has stated that “all vaccinations recognised as clinically safe can be used in good conscience”.22


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