#16,854
Early in the pandemic conventional wisdom held that once you have been infected with COVID, you were protected against reinfection - probably for years - and potentially forever. While there were reasons to question this `best case scenario' (see COVID-19: From Here To Immunity), many people believed we could `infect ourselves out of this pandemic'.
By the summer of 2020, reinfections - while rare - were beginning to appear, and their numbers only increased with the arrival of Alpha in late 2020, and Delta in the spring of 2021.
Vaccines, which were also expected to provide `durable' protection, were showing decreased longevity with the arrival of each new variant. `Breakthrough' infections, particularly after the emergence of Omicron, took off (see MMWR: Waning 2-Dose and 3-Dose Effectiveness of mRNA Vaccines Against COVID-19).
But even with this changing viral landscape many countries have set an arbitrary 60, 90, or even 180 day `window' following infection (or vaccination) where they assume a person is `protected', and re-testing for COVID is not generally recommended.
Last week, in EID Journal: Early SARS-CoV-2 Reinfections within 60 Days and Implications for Retesting Policies, we looked at multiple documented cases of reinfection (by different lab-confirmed variants) well within the 60-day window, and a call to re-evaluate these arbitrary (and optimistic) assumptions about the duration of immunity.
In light of these recent findings, yesterday New Zealand's Ministry of Health lowered their threshold for re-testing following COVID infection from 90 days to just 30 days.
I'll return with a postscript after the break.
Getting reinfected with COVID-19
The latest evidence shows that getting reinfected with COVID-19 can occur within a short period of time. Reinfection will become more likely as new variants spread among the community
Last updated: 30 June 2022We have updated our advice on getting infected again with COVID-19 after a previous COVID-19 infection and when people should take a rapid antigen test (RAT).
If a person develops new symptoms consistent with COVID-19, and it’s 29 days or more since a previous infection, it’s possible they have a reinfection with COVID-19 and they should test using a RAT.
This reflects a change from our earlier advice which was that people would not need to re-test if they had tested positive for COVID-19 within the past 90 days.
It is unclear how common it is to be reinfected with COVID-19. We are constantly monitoring international and national data and updating our reinfection guidance as new evidence becomes available.
Anyone reinfected with COVID-19 will have access to the same advice, help and support as they would receive for a new COVID-19 infection.
Advice for people who have had COVID-19 before and get new symptoms 28 days or less since your last infection
If COVID-19 symptoms return and it is 28 days or less since your last COVID-19 infection:there is no need to take a rapid antigen test (RAT) you should stay home and recover until 24 hours after you no longer have symptoms.
Some people recovering from COVID-19 may have symptoms that come and go for some time afterwards or they may be caused by other infections like the common cold, flu or a chest infection.
If you have an underlying health condition or your symptoms are getting worse, seek advice from a health practitioner or call Healthline on 0800 358 5453.
COVID-19 symptoms
29 days or more since your last infection
If you develop new COVID-19 symptoms and it is 29 days or more since your last COVID-19 infection:it is possible that you have COVID-19 again and you should take a RAT. if you test positive, this will be considered a reinfection and you should follow the standard COVID-19 isolation guidelines.
COVID-19 symptoms
Self-isolation requirements if you have COVID-19
Your household contacts will also need to isolate, unless they have either:had COVID-19 in the last 90 days and are recovered been a household contact in the last 10 days.
Isolation requirements for household contacts.
If your result is negative
If your result is negative, your symptoms could be another infection, such as the flu or another virus. If your symptoms continue you should repeat a RAT 48 hours later. If this is still negative, then stay at home until at least 24 hours after your symptoms resolve.
If you have an underlying health condition or symptoms that are getting worse, you should call Healthline on 0800 358 5453 or your local healthcare provider.
Reinfection with COVID-19 – what we know so far
Reinfection refers to the detection of a second or subsequent COVID-19 infection, regardless of the variant involved.
You are more likely to become reinfected as your immune response from the vaccine, or your previous COVID-19 infection, decreases over time.
It is still unclear how common reinfections are but they’re likely to become more common as new variants and subvariants spread across New Zealand.
For most people illness caused by reinfection is likely to be no more severe than a previous infection, but they can experience different symptoms.
Changing from 90 days to 29 days or more
Early in the COVID-19 pandemic, many countries chose to advise not to test within a 90-day period of an initial infection, when reinfection was thought to be unlikely and difficult to diagnose with PCR.
Evidence now shows that reinfection can occur within 90 days, particularly with new variants.
In recognition of this evidence our advice is now to test from day 29, if you experience new COVID-19 symptoms following a previous infection.
Within 29 days of a previous infection it is very difficult to diagnose reinfection because symptoms, viral levels and test positivity can continue to vary for some weeks following an infection with COVID-19.
Evidence on reinfections is evolving rapidly. We will continue to monitor emerging information on reinfection and update this advice as new evidence becomes available.
COVID-19 infection and immunity
Monitoring reinfection in the community
When someone uploads a positive RAT into My Covid Record, if it is 29 days or more since their last infection, they will be categorised as a reinfection and given the same advice and support as for a new infection.
Using this data from My Covid Record we can now monitor the number of people with a reinfection with COVID-19. Information on the number of reinfections will be included in the daily COVID-19 updates published on our website.
Latest COVID-19 current cases in New Zealand.
Guidance for clinicians
We have updated our clinical guidance for healthcare providers about how to manage patients who present with symptoms consistent with COVID-19, or a positive COVID-19 RAT, after a previous COVID-19 infection.
Guidance on reinfection for clinicians.
Downloads
Clinical guidance on testing for possible covid-19 reinfection (docx, 409 KB)
Clinical guidance on testing for possible covid-19 reinfection (pdf, 231 KB)
Everything we know about the BA.4/BA.5 Omicron variants (see NEJM: Neutralization Escape by SARS-CoV-2 Omicron Subvariants BA.2.12.1, BA.4, and BA.5) suggests they have an even greater ability to evade prior immunity, making `breakthrough infections' and reinfections even more likely in the months ahead.
The SARS-CoV-2 virus has shown a remarkable ability to adapt to humans (and other hosts), and as it has evolved its abilities have changed.
As the COVID threat changes, we need to be nimble enough in our response to pivot when needed, if we are to bring this pandemic under control.
Hopefully more countries will follow New Zealand's lead.
