The Delta variant is a highly contagious Sars-CoV-2 virus strain. Video / Paul Slater
Life during a Covid outbreak comes with a unique set of rules, some of which are not always clear. In the final instalment of this daily feature we answer questions from readers about anything Covid-related. Email covidquestions@nzherald.co.nz
My granddaughter has recently been worried that the Covid vaccination can cause infertility. She and her friends sourced this information I know not where but it has caused them some concern. Are you able to reassure them that this is just wrong information and the vaccination will not cause infertility? Shelagh G
There is no evidence the vaccine can cause infertility in men or women. In fact, studies have shown thousands of women vaccinated against Covid 19 have fallen pregnant in the months after receiving their shots.
Somewhere along the line the myth developed based on minor similarities between syncytin-1, an important protein in the placenta, and the coronavirus spike protein. Sceptics feared that meant the vaccine could mistakenly create antibodies which interfere with the development of the placenta.
However, the Immunisation Advisory Centre states on its website there is "no biologically plausible reason why this vaccine could have any effect on our genes or fertility".
"Upon injection, the lipid nanoparticle containing the mRNA is taken up by specialised cells (dendritic cells) at the injection site in the arm. These cells use the instructions from the vaccine mRNA to make only the Sars-CoV-2 spike protein and the mRNA degrades rapidly. The mRNA from the vaccine does not enter the nucleus of any cells," the website explains.
"Furthermore, it is highly unlikely that any active components of the vaccine or the spike protein produced will reach the ovaries or the testes. No vaccine-related effects on fertility or pregnancy were seen during preclinical studies."
In The Conversation, Instructor of Human Immunology at Emory University Matthew Woodruff explains the immune system has a series of checks and balances that are intended to prevent autoimmune attacks, which means antibodies rarely make mistakes.
"When B-cells – the cells in the immune system that produce antibodies – are first "born", they carefully screen themselves to make sure that they won't target the body's own organs. That self-screening continues as B-cells patrol the body looking for an infection to fight; if they find something potentially threatening, like a vaccine, they engage in a highly orchestrated dance with other immune cells," he writes.
"Through that weeks-long process, only B-cells that produce antibodies against the outside invader survive. B-cells with self-destructive potential are killed."
He explains that in very important parts of the body like the placenta and the brain, the threshold for activating the body's immune response is even higher.
Contracting Covid-19 itself, however, can lower a man's sperm count and cause erectile dysfunction and serious illness in pregnant women.
That's because the body rushes to defend itself when confronted with a severe infection and does not have the time to carefully select its antibodies, meaning some are likely to target healthy cells.
From the total number of hospitalisations, are there any partially or totally vaccinated? Trudy
None of the cases in the current Delta outbreak who were fully vaccinated for at least two weeks before testing positive have ended up in hospital.
But when a two-week gap since receiving a jab was taken into account, none of the fully vaccinated cases and only four people with one dose have been hospitalised.
That means 84 out of the 88 cases in hospital - or 95 per cent - had not had a single dose of the Pfizer vaccine more than two weeks before testing positive.
A spokesperson for the Ministry of Health said: "Many of these vaccinations were done just before the cases were detected, so the vaccinations may have happened after exposure to Covid-19."
This follows trends overseas where fully vaccinated people are much less likely to end up in hospital.
As of 8am on Wednesday, there were 855 cases so far in the outbreak: 702 were unvaccinated, 115 had one dose, and 38 had two doses.
Vaccinologist Helen Petousis-Harris told the Herald it was a reminder that two doses were needed to be most effective and that it took time for them to kick in.
She said two weeks after one jab, a person was about 77 per cent protected against serious disease from Delta. This jumped to the high 90s two weeks after a second dose.
Myocarditis after receiving the Pfizer vaccine is listed as an adverse event, and recently we have had an announcement of a woman dying of myocarditis, likely caused by the vaccine. My question relates to the mechanism that causes this. Has any research been done and do we have any tentative explanations? My curiosity arises because I know the Pfizer vaccine does not contain the virus itself, and the messenger RNA injected simply codes for the body to make the spike protein, which the body's immune system can then intercept and so learn how to make antibodies and killer cells against the spike protein, thus preventing viral particles from entering cells in the body in the future. So how does this process cause myocarditis? And in patients who contract Covid-19, is the myocarditis due to the spike protein rather than to the virus itself? Cathy M
Myocarditis, inflammation of the heart muscle wall, is a rare side effect of the Pfizer and Moderna vaccines and in most vaccine-related cases the inflammation was mild.
An Israeli study has found myocarditis occurred in 2.7 per 100,000 people vaccinated with the Pfizer vaccine. The same study found that the risk of myocarditis with Covid-19 was four times higher at 11 cases per 100,000 people infected with the virus.
Vaccinologist Helen Petousis-Harris said scientists had not yet determined why myocarditis seemed to be a side effect of the Pfizer vaccine.
She said it was probably a general inflammatory response similar to people getting a fever, headache or an aching body when the immune system sprung into action after receiving the vaccine.
In most cases, myocarditis was caused by a viral infection but she said that would not be the case with the vaccine.
It was unlikely the spike protein caused the problem either, she said.
"The spike protein is processed in the cells at the injection site."
In New Zealand there has been one death reported as being from myocarditis following vaccination. The case has been referred to the coroner who has yet to make an official determination on the cause of death.
Petousis-Harris said in most cases the person might need to be monitored in hospital for a few days but would make a full recovery.
While the woman's death was the first in New Zealand, so far five people in the European Union have died from the condition after 160 million vaccine doses.
