RESUMO
We hypothesized that reported SARS-CoV-2 infection numbers are underestimated and piloted a point prevalence by rapid antigen testing in the VACCELERATE volunteer registry. Between July-1 and July-7, 2022, 7/419 (1.67%) tests were positive. Compared to reports of the German Federal Government, our results suggest a 2.39-fold higher prevalence. Our findings imply that the actual prevalence of SARS-CoV-2 may be higher than detected by current surveillance systems, so that current pandemic surveillance and testing strategies need to be adapted.
RESUMO
Vaccines are the most important means to overcome the SARS-CoV-2 pandemic. They induce specific antibody and T-cell responses but it remains open how well vaccine-induced immunity is preserved over time following homologous and heterologous immunization regimens. Here, we compared the dynamics of humoral and cellular immune responses up to 5 months after homologous or heterologous vaccination with either ChAdOx1-nCoV-19 (ChAd) or BNT162b2 (BNT) or both. Antibody responses significantly waned after vaccination, irrespective of the regimen. The capacity to neutralize SARS-CoV-2 - including variants of concern such as Delta or Omicron - was superior after heterologous compared to homologous BNT vaccination, both of which resulted in longer-lasting humoral immunity than homologous ChAd immunization. T-cell responses showed less waning irrespective of the vaccination regimen. These findings demonstrate that heterologous vaccination with ChAd and BNT is a potent approach to induce long-term humoral and cellular immune protection. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSDue to some rare severe side effects after the administration of the adenoviral vaccine, ChAdOx1 nCoV-19, many countries recommended a heterologous vaccination scheme including mRNA vaccines like BNT162b2 for the second dose. We performed a PubMed search (with no restrictions on time span) using the search terms "SARS-CoV-2" and "heterologous vaccination" and obtained 247 results. Only a fraction of manuscripts included direct comparisons of patient cohorts that received either a heterologous or a homologous vaccination regimen. Of those, the vast majority investigated only short-term immunogenicity after vaccination. Thus, little is known about the long-term maintenance of immunity by heterologous compared to homologous vaccination. Added value of this studyWe add a very comprehensive and comparative study investigating heterologous and homologous vaccination regimens early and late after vaccination. Key features include the number of patients (n = 473), the number of vaccination cohorts (n= 3), the fact that samples were derived from three independent study centers and comparative analyses were performed at two independent study centers, as well as in-depth investigation of humoral and T cellular immunity. Implications of all the available evidenceThe recent data creates a line of evidence that heterologous vaccination, compared to homologous vaccination regimens, results in at least non-inferior maintenance of humoral and cellular immunity. The enhanced understanding of immunity induced by individual vaccination regimens is crucial for further recommendations regarding the necessity, timing and choice of additional vaccinations and public health policies.
RESUMO
Administration of a first dose of the COVID-19 vaccine ChAdOx1 nCoV-19 (Vaxzevria(R), AstraZeneca) is associated with a certain risk for vaccine-induced immune thrombotic thrombocytopenia. Therefore, several countries have recommended replacing the second dose of ChAdOx1 nCoV-19 with an mRNA-based vaccine as a precautionary measure, although data on safety and efficacy of such heterologous prime-boost regimen are sparse. Therefore, vaccinees, who had received a heterologous vaccination using ChAdOx1 nCoV-19 as prime and BNT162b2 (Comirnaty(R), BioNTech-Pfizer) mRNA as boost vaccination were offered SARS-CoV-2 antibody testing to quantify their vaccine-induced neutralizing antibody response5. The results were compared to cohorts of healthcare workers or volunteers, who received homologous BNT162b2 or homologous ChAdOx1 nCoV-19 vaccination regimens, respectively. A striking increase of vaccine-induced SARS-CoV-2 neutralizing antibody activity was observed in 229 vaccinees that received a BNT162b2 boost 9 to 12 weeks after ChAdOx1 nCoV-19 prime. In our cohort comprising over 480 individuals, the heterologous vaccination scheme induced significantly higher neutralizing antibody titers than homologous ChAdOx1 nCoV-19 and even than homologous BNT162b2 vaccination. This proves that a single dose of a COVID-19 mRNA vaccine after ChAdOx1 nCoV-19 prime vaccination is sufficient to achieve high neutralizing antibody levels predicting immune protection from SARS-CoV-2 infection, and may even increase vaccine efficacy offering an alternative in a setting of vaccine shortage.
