Various antibody 'kits' check for different antibodies. Some vaccines only produce anti spike antibodies: kits that are designed for N antibodies will show a negative result. Besides, some kits may not pick up low levels of antibodies. Quality variation in kits is an issue.
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Is there s difference in antibodies generated by natural infection and vaccine?
Natural infection produces a wide range of antibodies, of whom kits check mostly N type. Vaccines of mRNA or adenovirus vector type generate only Spike antibodies.
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Kits that detect N antibody will show negative result here. (Not all kits will tell us which antibody is being tested). Kits that check for spike antibody may turn positive, but that also depends on the sensitivity of the kit. Sometimes the Ab level might not trigger it.
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Antibodies are not reliable surrogates of immune protection from vaccines. Immunity is multi-pronged, most components of which (e.g. T cells) cannot be reliably quantified by present day technology.
In summary, a negative antibody test after vaccination proves nothing.
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Doing a test in clinical practice is generally to help with decision-making. If the antibody test result will not change our actions afterwards, it is better not to do the test.
Besides, a negative result in this setting can cause unjustified anxiety & disappointment.
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Why not do the test anyway "just to see if our body responded"?
Consider this: if the test is negative, it does not mean that the vaccine did not work, or that another vaccine must be tried in the future. If the test is positive, it could be from past infection or vaccine.
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In other words, a positive COVID serology test does not reliably distinguish a "protected" person from an "unprotected" person.
This is unlike the case of Hepatitis B vaccine, where we know that the presence of Anti HBS antibody after HB vaccination WILL provide protection.
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"Antibody tests currently authorized have variable sensitivity, specificity, PPV & NPV. They are not authorized for the assessment of immune response in vaccinated people. Furthermore, the serologic correlates of protection are not established"
EMA (European Medicines Agency) clears Astra-Oxford Vaccine
"The problems that have arisen in Austria in individuals after receiving AstraZeneca's corona vaccine were not caused by that vaccine"
-conclusion of European regulator for vaccines and medicines, EMA.
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"A 49-year-old woman in Austria died of severe blood clotting. Ten days earlier she had received the corona vaccine from AstraZeneca. A 35-year-old woman developed a pulmonary embolism from which she is now recovering"
"There were 2 more similar incidents. According to the EMA, this is not exceptional, it corresponds to the number of incidents among the general population. In Europe, 3 million people have been vaccinated with AstraZeneca, and 22 of them have had thrombosis or embolism"
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“The National Board of Health Denmark is now awaiting the EU drug authorities to investigate the possible connection between the COVID-19 vaccine from AstraZeneca and the serious cases of blood clots that have been reported”
“In six other European countries, the use of a specific batch of the AstraZeneca vaccine has currently been suspended pending investigations.
Unit Manager Tanja Erichsen encourages you to take it easy if you have been vaccinated with AstraZeneca's vaccine”
"I understand well if you are worried, but you must keep in mind that no connection has yet been established between the vaccines from AstraZeneca and the cases of blood clots. That is what we now want to investigate”
When an event occurs “following” vaccination it simply means it occurred in the days following the injection. It takes time for experts to investigate each event and determine the exact cause. The general public (& many healthcare professionals) do not know the difference.
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Deaths and illnesses occur in any population due to background rates.
But declaring that “AEFI occurred” unfortunately implies otherwise. Discretion must be followed while discussing this topic.
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Higher antibody level does not mean greater ability to neutralize the virus. This Italian paper finds that the strongest neutralization activity was shown by a patient who had the lowest antibody level detected by conventional serology assays.
Some basics:
Neutralization is the ability of the antibodies to inhibit growth of the virus. This is measured by looking at virus growth in lab cells, while bathed with serum containing antibodies - typically from those who are either recovered (convalescent) or vaccinated.
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Antibody titer, on the other hand, is measured by commercially available assays such as ELISA or CLIA .
Low levels might be marked as negative if below the detection limit of the assay. Manufacturer's claim of accuracy for these is often higher than real-life experience.
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3. Moderate-severe (Score 4) = 100% (CI 56-100) 4. Severe cases = 100%* (CI 17-100, *small no. of cases)
Better efficacy for the >21 days group than 14 days.
All ages showed same efficacy, but only 419 elderly were included in this study.
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Overall cases:
85/4953 in vaccine group
168/4870 in placebo group
This translates to 50.6%, but this is considered artificially low because of the fact that all participants were healthcare workers who, as a group, tend to over-report even the most minor symptoms.
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