BACK

Aviation worker tests positive for Covid-19 shortly after vaccination

Update

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 on Monday 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.

This article was published on
March 8, 2021

This explainer is more than 90 days old. Some of the information might be out of date or no longer relevant. Browse our homepage for up to date content or request information about a specific topic from our team of scientists.

Publication

What our experts say

Context and background

Resources

Media briefing

Media Release

Expert Comments: 

Dr Fran Priddy

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.

Professor Peter McIntyre

The main thing the vaccines do – and the main thing we want them to do – is to prevent people becoming ill, especially ill enough to need to go to hospital. Recent data from England and Scotland, where they have been rolling out both the Pfizer messenger RNA vaccine (the only one currently available in New Zealand) and the AstraZeneca “common cold” virus vector (vector) vaccine, show that both vaccines give significant (better than 50%) protection against hospitalisation or death due to COVID-19 to the most vulnerable people (those over 75 years) by 2 weeks after their first dose of vaccine and better than 85% by 4 weeks. However, preventing severe illness is different from preventing any infection due to the virus which causes COVID-19. We still do not know to what extent any of the vaccines prevent any infection and especially onwards transmission of the virus. It seems likely that transmission will be reduced, but unlike preventing severe disease, preventing transmission (which is a much bigger ask from the vaccine) may well require two doses and even in the best case scenario will not prevent ALL infection and transmission.

It is important to understand that what countries like NZ and Australia (where effectively the only infections occurring are amongst people coming from overseas) are aiming for is quite different from what countries like the UK or the US (where thousands of people are being hospitalised and tens of thousands infected every week) are aiming for. For Europe and North America, the vaccines will be doing a terrific job if they cause hospitalisations and deaths to come down steeply, which there are already signs they are doing with just a minority of the population (but most of the most vulnerable) vaccinated. For NZ, the only acceptable number of infections is zero.

Zero is a very demanding master with no room for error – if you want zero, then you must continue all measures as even the smallest chink in your armour is too large. Down the track, when all or almost all vulnerable people (and hopefully a large percentage of other adults) have been vaccinated, then “COVID free” countries like New Zealand will have to progressively decide how arrangements change: first, for travel within and between them and then for travel to the rest of the world. Ironically, for the COVID free countries, opening up to even some of the rest of the world which is not COVID free will mean that zero is no longer the only number. We all know that COVID is much worse than the worst influenza year for older and vulnerable people – that is why the “team of 5 million” has been prepared to accept the restrictions needed to stay at zero. And almost everyone agrees that zero has proven to be a successful strategy – certainly the rest of world thinks so. However, if, and hopefully when (courtesy of vaccines for the vulnerable) we get to a situation where COVID-19 really is not worse than influenza we can look forward to a COVID case being no more worthy of a place on the 6pm news than a case of influenza. Until that day, that is until we decide the benefits of opening up internally and externally greatly exceed the risks, then the same measures we have needed up until now to strive for zero will continue to be needed.

Professor Michael Plank

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.

Associate Professor Helen Petousis-Harris

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.

Dr Sarb Johal

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.

Associate Professor James Ussher

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.

Associate Professor Arindam Basu

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.

Dr Christopher Gale

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.

Q&A

No items found.