Historical COVID-19 antibody testing in dried blood spots (DBS)
Discontinued service - The Vitas COVID-19 antibody test, associated sampling kits and analytical service described on this page were offered during the COVID-19 pandemic and are no longer offered, sold or performed by Vitas. This page is retained solely as a historical record of Vitas’ previous analytical and research activities. It does not constitute a current commercial offer or instruction for use.
Vitas developed and validated a dried blood spot (DBS) test for IgG antibodies against SARS-CoV-2 based on the spike protein S1.
The test measured IgG antibodies produced following natural SARS-CoV-2 infection or vaccination with mRNA vaccines. It was designed to detect antibodies against the SARS-CoV-2 variants that had emerged before Omicron.
At the time, Vitas was investigating whether the assay also detected IgG antibodies produced following infection with the Omicron variant.
Commercial availability
During the COVID-19 pandemic, the test and associated sampling kits were made available through selected pharmacies and commercial partners. Vitas also supported testing programmes for organisations and research projects. The test, sampling kits and associated analytical services are no longer commercially available.
Customers purchasing more than 25 kits could contact Vitas AS directly. Payment could be made through Vipps or by invoice, and the kits could be shipped to the requested address.
Organizations and companies interested in screening employees could contact Vitas for an offer or a discussion regarding the use of the product and associated services.
It does not constitute a current commercial offer, advertisement or instruction for use.
The test
The test demonstrated a sensitivity above 94% and a specificity of 99.9% in a validation population of 601 individuals.
The testing solution included a CE-IVD-marked DBS collection kit and a CE-IVD-marked ELISA assay using the SARS-CoV-2 spike protein S1 as the antigen.
An extended validation involving 1,000 individuals was completed on 1 July 2020. The objectives were to evaluate the assay under routine conditions, obtain feedback regarding user-friendliness and investigate the prevalence of previous SARS-CoV-2 infection.
Fifty volunteers with confirmed positive SARS-CoV-2 PCR results submitted repeated DBS samples for IgG measurements. Based on these observations, the half-life of the measured IgG antibody concentration in blood was estimated to be approximately 110 days.
Use in Norwegian studies
The newly developed DBS antibody assay was used in two large Norwegian studies.
TRAIN study
The first study, named TRAIN, included approximately 3,400 participants associated with SATS fitness centres in Oslo in June 2020.
The objective was to investigate whether individuals who exercised inside fitness centres had a higher prevalence of COVID-19 infection than individuals who exercised outside.
The study found that very few participants tested positive for SARS-CoV-2 antibodies. No significant difference was observed in the proportion of positive samples between those who exercised indoors and those who exercised outdoors.
Corona and Immunity in Norway
The second study, named Corona and Immunity in Norway, included approximately 30,000 participants who were representative of the Norwegian adult population aged 16 years and older.
The study was conducted by researchers at the University of Tromsø during December 2020 and January 2021.
The highest prevalence of elevated SARS-CoV-2 antibody concentrations was observed among:
Participants aged 16–19 years: 1.9%
Participants born outside the Nordic countries: 1.4%
Participants living in Oslo: 1.7%
Participants living in Vestland: 1.4%
The results were subsequently reported in the study by Anda et al., titled Seroprevalence of antibodies against SARS-CoV-2 virus in the adult Norwegian population, winter 2020/2021: pre-vaccination period.
Vaccines and the IgG DBS test
The DBS assay used by Vitas detected IgG antibodies directed against the SARS-CoV-2 spike protein S1.
The spike protein was critically important for the virus because it enabled binding to and entry into human cells. Most COVID-19 vaccines used at the time were designed to stimulate antibodies and T-cell responses against the spike protein.
The Vitas DBS COVID-19 test was therefore used to evaluate antibody responses following vaccination with vaccines directed against the spike protein.
DBS sampling was considered particularly convenient during epidemics and was evaluated as a potentially useful method for assessing antibody responses to SARS-CoV-2 infection and vaccination.
Interpretation of results
Results were reported in arbitrary units (AU) through the Vitas reporting website. The results had to be interpreted in the context of the individual’s infection history, vaccination status, sampling time and other relevant clinical information.
| AU | Short evaluation | Explanation |
|---|---|---|
| 0-0.8 | Negative | Probably no infection or vaccine |
| 0.81-1.1 | Borderline | Perhaps infected/Vaccinated but antibody level is marginal |
| > 1.1 | Positive | Probably infected/vaccinated |
| 2-6 | Positive | Normal range after 1. vaccine |
| 5-11 | Postitive | Normal range after 2. vaccine and booster |
Background
In December 2021, the world remained affected by the most serious pandemic experienced in many decades.
At that time, more than 260 million people had been infected worldwide, and more than 5.2 million deaths had been reported among individuals infected with SARS-CoV-2.
To limit transmission, reduce the number of people requiring advanced hospital treatment and prevent health services from becoming overloaded, Norwegian and international authorities periodically introduced extensive restrictions.
These measures resulted in substantial social and economic consequences.
A large proportion of infected individuals experienced either no symptoms or only mild symptoms. Millions of people were required to remain in isolation or quarantine.
Individuals who had recovered from infection often developed partial or complete immune responses, which could reduce the risk of subsequent infection or serious disease.
A person infected with SARS-CoV-2 could remain infectious from several days to approximately three weeks.
Active infection was commonly detected using samples collected from the upper respiratory tract and analysed by polymerase chain reaction, or PCR.
After approximately three weeks, most individuals no longer had detectable virus in their airways. However, infection often left a biological trace in the form of antibodies directed against proteins from the virus.
The body generally began producing detectable antibodies approximately seven days after infection.
Immunoglobulin M, or IgM, was generally produced first, followed by immunoglobulin G, or IgG.
These antibodies could contribute to complete or partial protection against subsequent SARS-CoV-2 infection.
Limitations of antibody testing
Detection of IgM and IgG antibodies was initially considered a possible method for identifying individuals who might have developed some degree of immunity following infection.
However, antibody results alone were not sufficient to determine whether an individual was infectious, protected against reinfection or suitable for release from isolation or quarantine.
The relationship between antibody concentrations and protection changed as new SARS-CoV-2 variants emerged.
Different variants displayed different characteristics regarding transmission, immune escape and the risk of mild or severe clinical disease.
The Omicron variant appeared to be more transmissible than earlier variants and showed greater ability to evade immunity generated by previous infection or vaccination.
Provided that mutations did not substantially alter the relevant regions of the spike protein S1, the ELISA assay could detect antibodies produced following natural infection or vaccination.
Alternative sampling using DBS
Serum or plasma was commonly used for SARS-CoV-2 antibody testing.
Collection of serum or plasma required venous blood sampling by trained healthcare personnel, followed by centrifugation in a medical office or laboratory.
As an alternative, Vitas had performed analyses using dried blood spots for approximately 15 years.
A drop of capillary blood was collected from the fingertip and applied to specialised filter paper.
The sample could be collected by the individual at home or at work without assistance from healthcare personnel and subsequently sent to the laboratory by ordinary mail.
This approach was considered particularly useful during an epidemic because it reduced the need for physical attendance at a healthcare facility.
The sampling equipment could be sent directly to the participant or distributed through pharmacies, retailers or online channels.
This distribution model enabled large populations to be sampled at comparatively low cost.
The test demonstrated a sensitivity of approximately 94%. This meant that around six of every 100 previously infected individuals could receive a negative antibody result despite having experienced SARS-CoV-2 infection.
The specificity was close to 100%, meaning that false-positive results were uncommon in individuals who had not previously been infected.
SARS-CoV-2 variants
Viruses continually evolved as mutations occurred during replication.
Variants recognised during the pandemic included:
Alpha (B.1.1.7)
Beta (B.1.351)
Gamma (P.1)
Epsilon (B.1.427 and B.1.429)
Eta (B.1.525)
Iota (B.1.526)
Kappa (B.1.617.1)
B.1.617.3
Mu (B.1.621 and B.1.621.1)
Zeta (P.2)
Delta (B.1.617.2)
Omicron (B.1.1.529)
The Delta and Omicron variants received particular attention because of their rapid spread through large populations.
Both appeared to be more transmissible than the original Wuhan strain and the Alpha variant.
At the time, the severity of disease associated with the different variants remained under investigation.
By December 2021, laboratory studies indicated that three doses of an mRNA vaccine—two primary doses followed by a booster—could produce neutralising antibodies against the Omicron variant.
Preliminary clinical data also suggested that a booster dose of the BioNTech/Pfizer vaccine provided approximately 75% protection against symptomatic disease caused by Omicron.
However, observation periods were still short, and further information was required before firm conclusions could be drawn.
COVID-19 vaccines
Many research institutions and pharmaceutical companies invested substantial resources in developing safe and effective vaccines against COVID-19.
By August 2020, more than 200 vaccine candidates at different stages of development had been described.
Several countries, research institutions and pharmaceutical companies collaborated to accelerate vaccine development while evaluating efficacy and adverse effects in clinical studies.
Eight leading vaccine candidates were initially selected from different manufacturers and represented four different biological vaccine technologies.
Moderna and BioNTech/Pfizer developed vaccines based on messenger RNA encoding the SARS-CoV-2 spike protein.
The vaccines instructed the body’s own cells to produce the viral protein, which subsequently stimulated the immune system to develop antibodies and cellular immune responses.
Early studies involving both younger adults aged 18–55 years and older adults above 56 years showed that vaccination produced antibodies against the spike protein and stimulated type 1 T-helper-cell responses.
An important advantage of mRNA technology was that vaccines could be manufactured rapidly and at large scale without the need to cultivate the virus itself.
Large clinical studies involving tens of thousands of participants were subsequently conducted.
The mRNA vaccines developed by BioNTech/Pfizer and Moderna were among the first COVID-19 vaccines to receive regulatory authorization.
Initial studies indicated that they provided high levels of protection against infection, symptomatic disease, hospitalisation and death.
Most adverse effects were mild and temporary. Rare cases of myocarditis and pericarditis were subsequently reported, particularly among younger males.
By developing a DBS-based assay for antibodies against SARS-CoV-2, Vitas contributed to the analytical and sampling innovations introduced in response to the COVID-19 pandemic.
To learn more about our DBS analytical services, click here!