The science behind COVID-19 vaccines
In a recent NSWNMA webinar, Dr Jessica Stokes-Parish (PhD, RN), who works in an ICU, and Romy Blacklaw (IPN, RN), a clinical nurse in a COVID-19 vaccination hub, responded to common questions and concerns about COVID-19 vaccines.
Conventional vaccines can take three to 10 years to develop. In the case of COVID-19 vaccines, researchers and developers, backed by huge private and government funding, were able to work quickly and collaborate globally to develop a safe vaccine. Scientists built on decades of coronavirus research (e.g. SARS and MERS), recent advances in mRNA therapies (for cancer and viruses), and early identification of the genome sequence of SARS-CoV-2, to quickly develop potential vaccine candidates.
Both the AstraZeneca and Pfizer vaccines have had extensive safety testing. No shortcuts were made in what are acknowledged to have been gold standard vaccine trials. Tens of thousands of participants were enrolled in the clinical trials, some of the highest numbers ever seen.
Were COVID-19 vaccines rushed through?
The Therapeutic Goods Administration (TGA) provisionally approved COVID-19 vaccines after assessing all available data. Provisional approval is a process that allows temporary registration of promising new medicines and vaccines where the need for early access outweighs any potential risks. The TGA engaged early with pharmaceutical companies about their vaccines, assessing clinical trial data as it became available, rather than at the end of the three clinical trial phases. This sped up the review process.
What are the side effects of COVID-19 vaccines?
The Pfizer vaccine is generally well tolerated by most people, but side effects may include aches, pains and fever. While these effects are not very pleasant, they are a very good sign that your immune system is working. These symptoms are more common in younger people, who generally have more robust immune systems. Side effects are also more common after a second dose of the Pfizer vaccine. Most side effects occur within 24 hours of getting the vaccine, with symptoms typically resolving within 48 hours. AstraZeneca vaccine has similar side effects. Again, they are more likely to occur in those who are younger, and most side effects occur within 24 hours of getting a vaccine, with symptoms typically resolving within 48 hours.
What about adverse effects?
In any large-scale vaccination rollout, some people will experience a new illness or, sadly, pass away after vaccination. In some cases, these illnesses or deaths will be coincidental, and not caused by the vaccine. The TGA reviews all deaths reported in people who have received the vaccination, to assess whether the death was related to vaccine safety, or a side effect of the vaccine, or related to other causes.
A very rare adverse effect of the AstraZeneca vaccine is a rare type of blood clot – thrombosis with thrombocytopenia syndrome (TTS). Symptoms include nausea, blurred vision and pain in the head or legs that do not resolve with pain relief like paracetamol, and it is important to talk to your doctor immediately if you have any symptoms, as the condition is treatable. Fortunately, the risk of developing the syndrome is only 0.0002 per cent, based on the UK data.
In safety reports from the TGA, (as of 27 July), doses of the AstraZeneca vaccine given were 6.1 million, with six deaths. That gives a vaccine mortality rate of 0.00009 per cent. In contrast, in the same timeframe there were a total of 33,081 cases of COVID-19 infection in Australia, which resulted in 918 deaths – a case mortality rate of 2.78 per cent.
After any vaccine is registered and administered to people, experts and regulators continue to monitor vaccine safety in several ways. Australia’s safety monitoring is robust, including passive and active measures of surveillance. This safety information is publicly shared via AusVaxSafety.org.au and TGA.gov.au.
Why two doses of vaccine?
There is strong evidence that a second dose of either Pfizer or AstraZeneca increases your defence against COVID-19. Clinical trials show the Pfizer vaccine provides 52 per cent protection 12 days after the first dose, with protection rising to 95 per cent after the second dose. AstraZeneca vaccine protection against symptomatic COVID-19 was estimated to be 76 per cent at 22 days after the first dose, rising to 81 per cent when a second dose was given 12 weeks after the first. Pfizer and AstraZeneca both appear to offer less protection against the Delta variant than for the Alpha variant, and a second dose is even more important to protect against Delta.
Myths about COVID-19
Myth: the mRNA vaccines alter DNA
This is simply not possible. The mRNA vaccine cannot get into a cell’s nucleus. The flow of information from DNA to RNA to proteins – in that direction only – is one of the fundamental principles of molecular biology. The flow of information cannot go the other way, from mRNA to change DNA.
Myth: COVID-19 vaccines affect fertility and are dangerous during pregnancy
There is no mechanism for COVID-19 vaccines to affect fertility. The safety data on vaccines shows no fertility safety triggers. The animal data showed no fertility issues, and there was also no impact on sperm. On the other hand, vaccination has benefits to pregnancy and breastfeeding. We now have evidence that passive immunity occurs as a mother’s antibodies cross to the milk. Research has also shown immune transfer by the placenta for Pfizer, and the vaccine does not cause problems with the placenta. The COVID-19 disease, however, does cause problems during pregnancy. The risk of COVID-19, particularly the Delta variant, for pregnant people is quite significant. COVID-19 disease increases the likelihood of a preterm delivery, and the risk of pre-eclampsia or eclampsia.
Myth: Vaccines cause viral shedding
Viral shedding refers to a process where virus is shed by an infected person. For a virus to shed, it must be intact and actively reproducing. COVID-19 vaccines are not live; they contain no virus that is capable of reproducing, and the vaccine’s mRNA and viral vector are non-replicating.