COVID-19 Diary – Day 230

BBC Mis-Reports Antibody Data

An article from the BBC has been gaining a lot of traction online recently, with many people sharing it on social media. The article in question is headlined “Covid: Antibodies ‘fall rapidly after infection'”, and it claims that data released by the Office for National Statistics (in the UK) found that the number of people testing positive for antibodies has fallen by 26% between June and September.

Fortunately, this is a gross misinterpretation of the data and specifically goes against the text from the Office for National Statistics in their publication. The numbers in question do indeed drop 26%, but per the original data:

So the results do not show or imply a rapid decline of antibodies, they show that the pool of samples became larger, so a smaller percentage of people tested positive. There is no data in the document to suggest that antibodies are declining at a rapid pace. There are two relevant quotes about antibody decline, however:

There is a heavy push for new news and data when it comes to COVID-19, but it’s also very important to ensure that the news reported is accurate.

Robust Neutralizing Antibodies Persist for Months

A new study published just today is reporting some very positive findings regarding antibody longevity and effectiveness over time. Starting in March, over 72k individuals were screened for SARS-CoV-2 antibodies by the Mount Sinai Health System in New York, and as of October, over 30k had tested positive. Of these ~30k people, less than 5% required hospitalization or health intervention, the vast majority experienced only mild to moderate symptoms. The antibody concentration (titre) of each person’s blood was then tested, and broken into different concentration brackets as follows:

Low Titre:
1:80 – 690 People (2.29%)
1:16 – 1453 People (4.83%)

Medium Titre:
1:32 – 6765 People (22.49%)

High Titre:
1:960 – 9564 People (31.79%)
1:2880+ – 11610 People (38.60%)

This data gives us a very important piece of information about COVID-19 recovery, that the severity of the illness does not directly relate to the concentration of the proceeding antibodies. This implies (but can not specifically prove) that asymptomatic people and those who experience few or mild symptoms are not at increased risk of re-infection.

The study then took 120 blood samples, pulling from each of the concentration brackets, and tested them for neutralizing activity against authentic SARS-CoV-2 virus. The results are as follows:

As you can see the lower antibody concentrations, which represent ~7% of the blood samples, show successful neutralizing activity in approximately 50% of the tests. The other concentrations which represent the remaining ~93% of blood samples, show neutralizing activity 90-100% of the time. These tests imply that the vast majority of people who generate antibodies against SARS-CoV-2 will be immune to the virus afterwards.

The authors of the study then proceeded to run additional tests, choosing 121 of the participants, again representing each of the antibody concentration brackets, and had each of them submit 2 additional blood samples. The first additional blood sample was taken 52 to 104 days (84 mean) after symptom onset, and the second sample was taken 113 to 186 days (148 mean) after symptom onset. All the samples were tested, and the results can be seen here:

From the above data, you can see that patients with the higher and medium concentrations of antibodies typically dropped one concentration bracket over a period of ~5 months. Those patients with the lower concentrations initially saw an increase in concentration, and then saw their levels return to their previous bracket in the same time frame.

This data is extremely encouraging as it implies (but does not prove) that immunity to SARS-CoV-2 should last in most people for more than 5 months, and may even imply lasting immunity well beyond that time period.

The study also mentions that 3 of their 121 participants from the lowest bracket saw their antibody levels drop to the point where they no longer registered in the tests. So while the results shown here may represent most situations, there will also be outliers who do not produce antibodies at all, or who see their antibody levels drop quickly. Thankfully, these instances seem to be unusual.

That’s all for now, stay safe everyone!

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