Quantitative Analysis of SARS-CoV-2 Antibody Levels in Cancer Patients Post Three Doses of Immunization and Prior to Breakthrough COVID-19 Infections

(1) Background: COVID-19 vaccine effectiveness should be carefully evaluated and explicitly defined. To our knowledge, this is the first report to quantitatively evaluate humoral responses post 3 doses of SARS-CoV-2 immunization and prior to breakthrough COVID-19 infection in Canadian cancer patients. (2) Methods: In a prospective cohort study, we enrolled 185 cancer participants post COVID-19 vaccination in Kingston, Ontario, Canada. IgG antibodies against the SARS-CoV-2 spike receptor-binding domain were quantified by immunoassay post three doses of immunization. With the COVID-19 rapid antigen test and polymerase chain reaction (PCR), 16 breakthrough infections were identified. Results: Following SARS-CoV-2 vaccination (including BNT162b2, AZD1222, and mRNA-1273), the mean serum anti-spike protein antibody level was 197.2 BAU/mL (binding antibody unit, SD ± 393.9), 1335.9 BAU/mL (±3337.8), and 3164.8 BAU/mL (±6500.9) post the first, second, and third dose of vaccination. Observed differences were significant (p ≤ 0.001). The average antibody level of 3164.8 BAU/mL post the third dose was 89.9 times that of the seroconversion level (35.2 BAU/mL). This indicates that most vaccines approved are effective in producing robust antibody responses. In 11 breakthrough cases confirmed by PCR, prior to infection, the average antibody concentration was 3675.6 BAU/mL with the highest concentration being 9107.4 BAU/mL. Compared with this average antibody concentration of 3675.6 BAU/mL (104.4 times that of the seroconversion concentration), 0% of single dosed, 9.6% of double vaccinated, and 29.5% of triple vaccinated cancer patients had higher SARS-CoV-2 antibody levels. When patients were split into hematological and solid cancer, the hematological cancer group demonstrated lower serological responses than the solid cancer group in the first and second doses (first dose, average concentration 11.1 vs. 201.4 BAU/mL, respectively, p < 0.05; second dose, average concentration 441.5 vs. 1725.9 BAU/mL, respectively, p < 0.05). There was no difference in the third dose level (1756.3 vs. 2548.0 BAU/mL, p = 0.21). (4) Conclusions: Most vaccines were effective in producing robust antibody responses when more than one dose was given, and the more doses the higher the serological response. Likely due to the highly contagious nature of SARS-CoV-2 variants, a significant number of participants had SARS-CoV-2 antibody responses lower than the average antibody concentration prior to the known breakthrough infections. Additional vaccination is likely required to ensure immunity against infection by SARS-CoV-2.

Another piece of the Zika puzzle: assessing the associated factors to microcephaly in a systematic review and meta-analysis

BACKGROUND

Although it is known that Zika virus (ZIKV) infection during pregnancy may lead to microcephaly in the fetus, the prognostic factors associated with this tragic disorder remain unclear. We conducted a systematic review and meta-analysis to assess the prognostic factors associated with the incidence of microcephaly in congenital ZIKV infection.

METHODS

We conducted a comprehensive search in Ovid MEDLINE, Ovid MEDLINE (R) Epub ahead of print, Embase, Embase Classic, Web of Science, CINAHL, Cochrane CENTRAL, LILACS, and various thesis databases to identify human studies reporting microcephaly associated with congenital ZIKV infection. We requested primary data from the authors of the included studies to calculate summary estimates and conduct the meta-analysis of the most prevalent factors.

RESULTS

We screened 4106 titles and abstracts, and identified 12 studies for inclusion in the systematic review. The assessment of ZIKV infection and the definition of microcephaly varied among studies. A total of 6154 newborns/fetuses were enrolled; of those, 1120 (18.20%) had a diagnostic of ZIKV infection, of which 509 (45.45%) were diagnosed with microcephaly. Nine studies addressed the link between congenital ZIKV infection and neurological findings in newborns/fetuses. Half of the studies provided primary data. Three out of 11 factors of interest seem to be prognostic factors of microcephaly: infant's sex - males compared to females: Relative Risk (RR) 1.30, 95% Confidence Interval (95% CI) 1.14 to 1.49; the stage of pregnancy when infection occurred - infection in the first trimester of pregnancy compared to infection at other stages of pregnancy: RR 1.41, 95% CI 1.09 to 1.82; and asymptomatic infection compared to symptomatic infection during pregnancy: RR 0.68; 95% CI 0.60 to 0.77.

CONCLUSION

Our findings support the female-biased resistance hypothesis and reinforce the risk associated with the stage of pregnancy when ZIKV infection occurs. Continued surveillance of ZIKV infection during pregnancy is needed to identify additional factors that could contribute to developing microcephaly in affected fetuses.

PROTOCOL REGISTRATION

This systematic review was registered with the International Prospective Register of Systematic Reviews (PROSPERO), registration no. CRD 42018088075.