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Aviation Worker Tests Positive For Covid-19 Shortly After Vaccination – Expert Reaction
An Air New Zealand flight attendant tested positive for Covid-19 on Sunday, shortly after receiving a shot of the Pfizer vaccine.
Prime Minister Jacinda Ardern said this morning the vaccine takes a couple of weeks to work, so they wouldn't have expected the person to be protected from the virus.
The SMC asked experts to comment. Feel free to use these comments in your reporting or follow up with the contact details provided.
Dr Fran Priddy, Clinical Director Vaccine Alliance Aotearoa New Zealand – Ohu Kaupare Huaketo, comments:
"This is a critical point - we don't know how effective any of these vaccines are at preventing infection. We know they are effective at preventing disease, hospitalisation and death. So even vaccinated people need to keep up with routine COVID prevention measures. They could still become infected and spread to others. We should have better information on how well the vaccines prevent spread in the near future, but for now everyone needs to follow the same preventive measures."
Conflict of interest statement: Dr Priddy is Clinical Director of the Government-funded Vaccine Alliance Aotearoa New Zealand – Ohu Kaupare Huaketo, a partnership between the Malaghan Institute, the University of Otago and Victoria University of Wellington.
Professor Michael Plank, Te Pūnaha Matatini and University of Canterbury, comments:
"It’s most likely that this latest case caught the virus while overseas or on the flight back to New Zealand, before they received their first dose of the vaccine. The results from genome sequencing will help confirm this when they become available. It takes a few weeks for the protection offered by the vaccine to kick in and, for the Pfizer vaccine used in this case, the full level of protection requires a second dose. So it is not surprising that this person tested positive after being vaccinated. It is not possible to be infected by a vaccine because the jab does not contain any live virus. It only contains 'instructions' for our body’s immune system for how to fight off the virus.
"This case is a good reminder that vaccines, although incredibly useful and important, are not 100% effective and take a while to take effect. We know vaccines prevent people getting ill with COVID-19, but we are still waiting for more data about the level of protection they offer against getting infected. It is possible that some people will still get infected after being vaccinated and may even spread the virus to others. All this means that people still need to follow the relevant public health guidelines even after being vaccinated. This is necessary to protect the wider community, including those who haven’t yet been vaccinated or can’t be vaccinated for some reason. Until we build up a high level of population immunity, New Zealand will still be vulnerable to a major COVID-19 epidemic, so for now we need to maintain the elimination strategy."
No conflict of interest declared.
Associate Professor Helen Petousis-Harris, Vaccinologist, University of Auckland, comments:
"After you are vaccinated it takes the body at least a week to get those protective antibodies pumping out so you won’t be protected straight away. Full protection won’t occur until at least a week after your second dose. Also, while most people who get the vaccine will be well protected, there will be a few people who do not respond as well. Keeping up our other COVID-prevention behaviours will go hand in hand with vaccination for a while as long as this virus is widely circulating out there.
"When a person gets the first dose of vaccine the immune system kicks in almost straight away. However it takes a few days before the protection starts to kick in. This is because your body needs to alert and gather the various specialised cells needed to make the COVID-specific cells and antibodies. Once these are assembled immunity grows over time. After about two weeks you can expect some reasonable protection and once the second dose has been given full protection should have developed in over 9/10 people about a week later.
"The vaccine cannot cause any infection, there are no viruses or any other infectious material in the vaccine. In fact, this vaccine has been made entirely without the virus."
Conflict of interest statement: Helen is a member of the COVID-19 Immunisation Implementation Advisory Group (IIAG).
Dr Sarb Johal, psychologist, comments:
"The coverage of the vaccine is good but not perfect. The more people who take the vaccine, the better community level coverage we get. It will take time to get enough people in the community vaccinated to a highly significant level of protection. It’s also important to know that your immune system does not respond immediately after you receive the vaccine: it a gradual immune response that can give you some protection after 2-3 weeks: but even then, it is not an impregnable shield meaning you can forget all other protections we need to keep in place at times.
"When the risk level rises and Alert Levels are changed, we need to remember that the vaccine is best thought of as an additional layer of protection. Physical distancing, masking, continued washing of hands and tracking our movements are key behaviours that help to keep us safe. If we rely on the vaccine alone to protect, we are arguably making ourselves more vulnerable rather than safer. This is because some variants of the vaccine seem able to break through the immunity offered by the vaccine. We need to continue to guard against this risk.
"The vaccine is not a silver bullet for for the pandemic. How we use our multiple range of protections according to the risk that is still present and will endure for some time is going to be critical in keeping each other and ourselves safe. Vaccines are just one part of the multiple layers we are going to need to use for a considerable period of time.
"The good news is that these are small actions that can add up to a high level of protection, that continue to help us to avoid the worst outcomes we have seen in other places."
No conflict of interest declared.
Associate Professor James Ussher, Department of Microbiology and Immunology, University of Otago, comments:
"This case highlights a weakness in NZ's border. Air crew are working in a high risk environment without full personal protective equipment. While there are currently risk mitigation measures in place, both during air travel and at overseas destinations, these are insufficient to prevent infection, as demonstrated by this case. In addition to vaccination of air crew, procedures should be reviewed and tightened to reduce the risk of introducing the coronavirus to New Zealand. This should include re-consideration of the isolation period for air crew on return to New Zealand and the frequency of the testing regimen.
"While vaccination is highly effective at preventing infection that results in symptoms and is likely to be effective at preventing asymptomatic infection and reduce the risk of transmitting infection to others, it is not 100% protective. The degree of protection against asymptomatic infection and reduction in transmission to others is yet to be determined. Given the implications for transmission if Covid-19 were to be introduced into the community, vaccination of border-facing workers will not remove the need for them to continue to use personal protective equipment, practice good infection control, and to undergo regular surveillance testing.
"The Pfizer COVID vaccine has been shown to provide some protection against symptomatic infection from 12 days after the first dose, increasing to 95% protection from 7 days after the second dose. Administration of the vaccine after infection is very unlikely to provide any protection against the development of symptoms and disease. In this case, the flight attendant would have been infected prior to arrival in New Zealand and prior to vaccination.
"We are fortunate that this occurred during Auckland's level 3 lockdown."
Conflict of interest statement: Associate Professor Ussher is Science Director of the Government-funded Vaccine Alliance Aotearoa New Zealand – Ohu Kaupare Huaketo, a partnership between the University of Otago, the Malaghan Institute and Victoria University of Wellington. He is also on the Government Vaccine Taskforce’s Science and Technical Advisory Committee.
Associate Professor Arindam Basu, College of Education, Health & Human Development, University of Canterbury, comments:
"More frequent testing of aviation workers/border workers is likely to be useful for earlier diagnosis of positive persons, so such an action is justified on logic.
"A person can test positive even after vaccination, there is nothing unexpected in that, and that in no way shows that the vaccine is ineffective. There are several reasons for this:
From the time of first infection, it takes anywhere between 0-14 days for the manifestation of COVID-19 to turn out positive, with an average of 5-7 days, and this is regardless of vaccination. So, after the first dose of vaccine, or even after the second dose of vaccine (although that would be less probable, but possible), one can turn out to be positive.
No vaccine is 100% effective. The first dose of the Pfizer/BioNTech vaccine is about 50% protective, but improves to about 90% in trials after the second dose. However a trial result and what happens in the community may not always match, so conferral of protection after the first dose is not that great.
The PM is correct that the vaccine takes a couple of weeks to work.
There is no clear evidence whether the vaccine will prevent Covid infection, but if someone is infected, then the presence of antibodies raised against the vaccines administered prior will protect an individual. Hence, even with vaccination, some people may still show positive results.
"For these reasons, regardless of vaccination status, the usual precautions are necessary: mask, hand-washing, cough/respiratory hygiene, distance, use of COVID19 contact tracing app usage.
"With the vaccination, there is a need for careful mass education that one does not become immune the moment they get the first jab. While the vaccine itself is safe and effective, these things take time, one needs to be patient. While the immunity develops, it is necessary for everyone, regardless of vaccination status, to take necessary precautions. Then, once a substantial proportion of the population gets the immunisation and - assuming no new super virulent strain emerges - things get better."
No conflict of interest declared.
Dr Christopher Gale, Senior Lecturer, Department of Psychological Medicine, University of Otago, comments:
"People who have been keeping to the rules can still get COVID. It is a virus. The virus does not care how well you wore a mask or social isolated: those may decrease your risk, but not eliminate it.
"A vaccine works by inducing an immune reaction. This means two things: the first is that until you have had that immune reaction you are still vulnerable to the virus, and you will, if the vaccine works, be positive for some antibodies. An example: I got the Hepatitis B vaccine as soon as it was available as a house surgeon, and before it was funded. I am, some three decades later, still producing antibodies, and don't need a booster.
"People who travel to places where there is COVID are more likely to get COVID. The good news is that eventually we will have herd immunity COVID, but that will either take most of the population being vaccinated or most of the population being infected. At present neither are happening."
No conflict of interest declared.
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