PCR rapid test variants

26 July 2021 Newsletter

Unfortunately, there is once again a lot of disquiet regarding SARS-CoV-2. The Netherlands has turned red on the European map due to the number of new infections. The much-discussed reproduction rate has exceeded 2 for the first time in a long time. The vast majority of new cases are currently among young people who, thankfully, do not generally become so ill as to require hospitalisation. Other age groups have not yet seen a significant increase in new infections. Whether this will continue to be the case given the increasing number of fully vaccinated persons is now the question on everyone’s mind. Fortunately, hospitals haven’t yet experienced a substantial increase in the number of admissions, although there have been reports here and there that it seems to be getting busier again.

These developments have of course led to a lot of questions about the role played by newer variants, such as the delta variant. How infectious is/are these exactly? And how protective is vaccination, both in preventing serious illness and/or death and in protecting against (new) infections? Regarding the latter, there are an increasing number of reports of people who become infected despite having been fully vaccinated. This is also being seen in neighbouring countries. The severity of the disease appears to be generally much less in those cases but it is, of course, true that these people potentially contribute to the spread of the disease during the period that they are carrying the virus, even if they are not very ill with it themselves.

Does this have consequences for the testing policy? In the Netherlands, the advice is once again to be very cautious about relying on rapid tests and instead to use PCRs in particular. There are two important reasons for this. The first is that PCRs can be used in the laboratory to determine which virus strain is involved, something that is not possible with an antigen rapid test. This means PCR testing serves an additional ‘surveillance’ function. The second reason is that it has been shown that the amount of virus carried by (fully) vaccinated persons is often considerably lower. The chance of missing infections with a less sensitive antigen rapid test is real and is supported by our own experience in the hospital.

We would like to share some thoughts with you:

  1. Perhaps needless to say, at present people are considered immune (or rather as immune as possible, because guaranteed and complete protection is unfortunately not achievable, as we know!) if they:
  • have completed a full vaccination series more than 14 days ago
  • have experienced COVID-19 and received 1 vaccination more than 14 days ago
  • have experienced COVID-19 in the last 6 months
  1. A (breakthrough) infection in a person who is considered immune on the basis of the above criteria may manifest itself with very few or no symptoms. However, the virus is present in these people, and they must be considered contagious at that moment. Paradoxically, when the quantity of the virus is lower (and thus the infectiousness probably also), there is a risk that such a person will infect more people because he or she does not have any symptoms and therefore continues to participate in social life.
  2. If, in the above situation, such a person becomes infected with a more contagious variant, such as the delta variant that is rapidly gaining dominance in the Netherlands, this problem will only increase.
  3. Another danger has already been mentioned: due to the lower amount of virus in this group, there is a big chance that a COVID antigen rapid test is false-negative. Vaccinated individuals should therefore be subjected to a PCR if the virus is to be detected.
  4. At the moment it is unknown how much damage the currently circulating variants can cause among vaccinated persons. Our impression is that the majority of these people will have few complaints and will not end up in hospital.

With these 5 things in mind, we would like to mention three situations:

I. A heterogeneous group of (a) vaccinated and (b) unvaccinated persons working together on a project where 1.5 meters distance is not achievable
Group a can infect group b, especially if the symptoms experienced by people in group a are not as bad as expected and are not recognized in time. Our advice is to carry out SARS-CoV-2 screening in such a mixed group by means of PCR tests. As mentioned above if, at a later stage, people develop symptoms, a PCR test is strongly preferred

II. A homogeneous group of vaccinated persons together in a bubble
In this group, the risk of mutual infection is clearly reduced. So far it seems that in general the severity of any infection among previously vaccinated people is also lower. Such a group is therefore obviously the most optimal situation. If you still want to screen this group for valid reasons (for example: remote location of the project, too high a cost-of-error of missing SARS- CoV-2) then PCR is the screening test of choice. This also applies to anyone experiencing (suspected) symptoms!

III. A homogeneous group of unvaccinated people together in a bubble
If screening for SARS-CoV-2 is desired, there is certainly a place for rapid tests in this group. A PCR remains more reliable – something that cannot be stressed enough. If people with symptoms are found in such a cohort, they should be re-tested as soon as possible, both in their own interest and from the point of view of the rest of the (most vulnerable) group. In such a case, a PCR is again much preferred.

We could go into more detail about these and other scenarios, but hopefully this provides you with some guidance on the most common situations.

If you have any questions at all, please contact us at world@travelclinic.com. During opening hours, we can also be reached by phone on 010-8201120. For more information, please visit our website corporate.travelclinic.com.

At weekends we are open for COVID-19 testing by appointment from 09:00-11:00.

Kind regards on behalf of our Management Team, Dr Lennert Slobbe, internist-infectiologist


Leave a Reply

Your email address will not be published. Required fields are marked *