Cross-Reactivity between Half Doses of Pfizer and AstraZeneca Vaccines-A Preliminary Study.

Media reports have caused a significant drop in confidence in the AstraZeneca ChAdOx1 nCoV-19 COVID-19 vector vaccine (Vaxzevria, AstraZeneca Södertälje, Sweden). This has caused many people, already vaccinated with the first dose of AstraZeneca, to refuse vaccination with this product. On the other hand, the increased demand for mRNA vaccines has resulted in a greater shortage of mRNA vaccines and cases of people being vaccinated with the AstraZeneca vaccine after the first dose of the Pfizer/BioNTech BNT162b2 COVID-19 vaccine (Comirnaty, Pfizer/BioNTech, Mainz, Germany). Moreover, currently, 60.9% of the global population have received at least one dose of a COVID-19 vaccine, while only 10% of people in low-income countries have received at least one dose. Even less people are fully vaccinated. The present pilot study evaluated the administration of half doses of AstraZeneca and Pfizer vaccines and included the enrollment of 26 subjects who were vaccinated with a different vaccine the first and second time. The reference group included individuals undergoing vaccination with two full doses of the Pfizer vaccine (21-day interval) monitored for their antibody levels as part of a parallel study. The distribution of antibody levels was not significantly different between those who received the Pfizer vaccine alone and those receiving the AstraZeneca vaccine plus Pfizer or Pfizer and AstraZeneca. To prepare for the next pandemic waves, solving the problem of the matching of booster vaccine to the previously received doses would be advisable. The topic is important and emerging as most of the population in low-income countries is still not vaccinated. We strongly believe that vaccine equity is the most important aspect of vaccination strategies.

Cross-Reactivity between Half Doses of Pfizer and AstraZeneca Vaccines-A Preliminary Study

Media reports have caused a significant drop in confidence in the AstraZeneca ChAdOx1 nCoV-19 COVID-19 vector vaccine (Vaxzevria, AstraZeneca Södertälje, Sweden). This has caused many people, already vaccinated with the first dose of AstraZeneca, to refuse vaccination with this product. On the other hand, the increased demand for mRNA vaccines has resulted in a greater shortage of mRNA vaccines and cases of people being vaccinated with the AstraZeneca vaccine after the first dose of the Pfizer/BioNTech BNT162b2 COVID-19 vaccine (Comirnaty, Pfizer/BioNTech, Mainz, Germany). Moreover, currently, 60.9% of the global population have received at least one dose of a COVID-19 vaccine, while only 10% of people in low-income countries have received at least one dose. Even less people are fully vaccinated. The present pilot study evaluated the administration of half doses of AstraZeneca and Pfizer vaccines and included the enrollment of 26 subjects who were vaccinated with a different vaccine the first and second time. The reference group included individuals undergoing vaccination with two full doses of the Pfizer vaccine (21-day interval) monitored for their antibody levels as part of a parallel study. The distribution of antibody levels was not significantly different between those who received the Pfizer vaccine alone and those receiving the AstraZeneca vaccine plus Pfizer or Pfizer and AstraZeneca. To prepare for the next pandemic waves, solving the problem of the matching of booster vaccine to the previously received doses would be advisable. The topic is important and emerging as most of the population in low-income countries is still not vaccinated. We strongly believe that vaccine equity is the most important aspect of vaccination strategies.

Humoral Response after Vaccination with Half-Dose of BNT162b2 in Subjects under 55 Years of Age.

In the context of the ongoing COVID-19 pandemic, using a half-dose schedule vaccination can help to return to normalcy in a cost-efficient manner, which is especially important for low and middle-income countries. We undertook a study to confirm that in adults up to 55 years old, the humoral response to the half-dose (15 µg, 35 participants between 18 and 55 years old) and to the recommended dose (30 µg, 155 participants) in the two-dose three-week interval schedule would be comparable. Antibody levels were measured by the Elecsys Anti-SARS-CoV-2 S assay (Roche Diagnostics, upper detection limit: 2570 BAU/mL) on the day of dose 2 of the vaccine and then 8-10 days later to assess peak response to dose 2. The difference in proportions between the participants who did and did not exceed the upper detection limit 8-10 days after dose 2 was not statistically significant (p = 0.152). We suggest that a half-dose schedule can help to achieve widespread vaccination coverage more quickly and cheaply.

Humoral Response to SARS-CoV-2 Vaccine of a Patient Receiving Methotrexate Treatment and Implications for the Need of Monitoring.

We report a case of monitoring the antibody response to the BioNTech-Pfizer vaccine of a 50-year-old female diagnosed with rheumatoid arthritis undergoing treatment with methotrexate (MTX). Antibody levels were measured 21 days after dose 1 (i.e., on the day of dose 2) and then 8, 14 and 30 days after dose 2 with Elecsys Anti-SARS-CoV-2 S assay (Roche Diagnostics). Patient showed a negative result after dose 1 and had the serum sample retested using a LIAISON® SARS-CoV-2 TrimericS IgG assay (DiaSorin), which showed a positive result. Subsequent samples were tested using both assays. Antibody levels kept increasing but at a much slower rate than in patients not receiving any immunomodulatory therapies. Other research indicates that among patients with autoimmune diseases, those receiving disease-modifying antirheumatic drugs (DMARDs) have higher COVID-19 mortality than those treated with tumor necrosis factor inhibitors (TNFis). These results indicate the need for people with autoimmune diseases to be carefully observed following vaccinations, including testing of antibody levels, and treated as potentially at risk until the effect of vaccination is confirmed. The different available vaccines should also be tested to verify their usefulness in the case of people with autoimmune diseases and those who take different immunomodulatory medications.

Usefulness of IVD Kits for the Assessment of SARS-CoV-2 Antibodies to Evaluate the Humoral Response to Vaccination.

BACKGROUND: The introduction of the vaccination against SARS-CoV-2 infection creates the need for precise tools for the quality control of vaccination procedures, detection of poor humoral response, and estimation of the achieved protection against the disease. Thus, the study aimed to compare the results of the anti-SARS-CoV-2 tests to evaluate the application of the WHO standard unitage (the binding antibody units; BAU/mL) for a measurement of response to the vaccination. METHODS: Patients undergoing vaccination against SARS-CoV-2 with Pfizer/BioNTech BNT162b2 (BNT162b2) (n = 79), referred for SARS-CoV-2 antibody measurement prior to vaccination and 21 days after dose 1, and 8, 14, and 30 days after dose 2 were included. The sera were tested with three assays: Elecsys SARS-CoV-2 S (Roche), LIAISON® SARS-CoV-2 TrimericS IgG (DiaSorin), and SARS-CoV-2 IgG II Quant (Abbott). RESULTS: The three assays showed varying correlations at different time points in the study. The overall agreement for all samples was moderate to high (ρ = 0.663-0.902). We observed the most uniform agreement for the day of dose 2 (ρ = 0.775-0.825), while it was least consistent for day 8 (ρ = -0.131-0.693) and 14 (ρ = -0.247-0.603) after dose 2. The dynamics of changes of the SARS-CoV-2 antibody levels in patients without history of prior SARS-CoV-2 infection appears homogenous based on the Roche results, more heterogenous when considering the DiaSorin results, and in between for the Abbott results. CONCLUSIONS: The results highlight the need for further work on the international standard of measurement of SARS-CoV-2 Ig, especially in the era of vaccination. The serological assays can be useful to detect IgG/IgM antibodies to assess the response to the vaccination. However, they cannot be used interchangeably. In terms of the evaluation of the immune response to the BNT162b2 vaccine, Roche and Abbott kits appear to be more useful.