#14,448
Over the past couple of months its been hard to find any reputable research indicating that SARS-CoV-2 infection leaves behind a robust and long lasting immune response in recovered cases. In fact, most of what we've seen has suggested the opposite; that post-infection immunity markers wane quickly.
- Five days ago, in EID Journal: Antibody Profiles According to Mild or Severe SARS-CoV-2 Infection, we saw a report indicating that patients with mild disease tended to mount a slower and less robust IgG antibody response.
- In July (see Kings College: Longitudinal Evaluation & Decline of Antibody Responses in SARS-CoV-2 infection), researchers reported that `the magnitude of the nAb response is dependent upon the disease severity'. They also found a significant percentage of mild cases saw their nAb titers drop to near baseline within 60 days post-infection.
- Also in July, the Journal Nature published Antiviral antibodies peter out within weeks after infection - which stated `Key antibodies that neutralize the effects of the new coronavirus fall to low levels within months of SARS-CoV-2 infection, according to the most comprehensive study yet.'
- Concerns that were bolstered a little over 2 weeks ago, in CDC Clarifies: Recovered COVID-19 Cases Are Not Necessarily Immune To Reinfection.
The way we typically measure potential post-infection immunity - using virus specific neutralizing antibody (nAb) titers - doesn't necessarily tell the whole story, however.
As I've written before - nAb titers aren't the only measure of potential post-infection immunity - and the role of T-Cells and other aspects of the innate immune system in fighting this virus are poorly understood.
So its possible, even without long-lasting nAbs, some people may become immune to SARS-COV-2.
All of which brings us to a new study, published this week in the New England Journal of Medicine (NEJM), which examines the antibody levels remaining in over 1200 recovered COVID-19 cases living in Iceland, and found most (91%) maintained robust levels of antibodies 4 months later.
Whether or not these antibody levels are protective against reinfection - and for how long - isn't known. But at least this study suggests their levels may not wane as quickly as previously reported.
As always, this is just one study, and it doesn't necessarily negate the immunity concerns raised by other research teams over the past few months. Follow the link to read the study in its entirety. I'll have a brief postscript when you return.
Daniel F. Gudbjartsson, Ph.D., Gudmundur L. Norddahl, Ph.D., Pall Melsted, Ph.D., Kristbjorg Gunnarsdottir, M.Sc., Hilma Holm, M.D., Elias Eythorsson, M.D., Ph.D., Asgeir O. Arnthorsson, M.Sc., Dadi Helgason, M.D., Ph.D., Kristbjorg Bjarnadottir, Ph.D., Ragnar F. Ingvarsson, M.D., Brynja Thorsteinsdottir, B.Sc., Steinunn Kristjansdottir, B.Sc., et al.September 1, 2020DOI: 10.1056/NEJMoa2026116
Abstract
BACKGROUNDLittle is known about the nature and durability of the humoral immune response to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).METHODS
We measured antibodies in serum samples from 30,576 persons in Iceland, using six assays (including two pan-immunoglobulin [pan-Ig] assays), and we determined that the appropriate measure of seropositivity was a positive result with both pan-Ig assays. We tested 2102 samples collected from 1237 persons up to 4 months after diagnosis by a quantitative polymerase-chain-reaction (qPCR) assay. We measured antibodies in 4222 quarantined persons who had been exposed to SARS-CoV-2 and in 23,452 persons not known to have been exposed.RESULTS
Of the 1797 persons who had recovered from SARS-CoV-2 infection, 1107 of the 1215 who were tested (91.1%) were seropositive; antiviral antibody titers assayed by two pan-Ig assays increased during 2 months after diagnosis by qPCR and remained on a plateau for the remainder of the study. Of quarantined persons, 2.3% were seropositive; of those with unknown exposure, 0.3% were positive. We estimate that 0.9% of Icelanders were infected with SARS-CoV-2 and that the infection was fatal in 0.3%. We also estimate that 56% of all SARS-CoV-2 infections in Iceland had been diagnosed with qPCR, 14% had occurred in quarantined persons who had not been tested with qPCR (or who had not received a positive result, if tested), and 30% had occurred in persons outside quarantine and not tested with qPCR.CONCLUSIONSOur results indicate that antiviral antibodies against SARS-CoV-2 did not decline within 4 months after diagnosis. We estimate that the risk of death from infection was 0.3% and that 44% of persons infected with SARS-CoV-2 in Iceland were not diagnosed by qPCR.
As I've written many times, conflicting scientific studies are nothing new, and individual studies can be misleading, particularly if other results are not weighed against it.
- Last April, in When Studies Collide (COVID-19 Edition), we looked at some wildly different `conclusions' regarding the level of acquired community immunity in the UK and Austria.
- In 2016, in When Flu Vaccine Studies Collide, we looked at widely differing assessments on the effectiveness of the nasal spray (LAIV) flu vaccine from here in the United States and elsewhere in the world.
- While in 2010, in When Studies Collide (Revisited), we looked at conflicting research on the efficacy of N95 respirators vs surgical masks, the effectiveness of Tamiflu (r) in treating influenza, and the dueling studies over whether seasonal flu shots can reduce the risk of heart attack and strokes.
While today's report from the NEJM is welcomed as potentially good news, we'll need to see additional corroboration - and proof that elevated nAb titers are protective against reinfection - before its time to celebrate.
