Read the important research studies below associated with transmission of viral load:
IMPORTANT HISTORICAL TRANSMISSION AND SPREAD (Wuhan strain never made it out of China / Asia) – History of the COVID-19 pandemic: Origin, explosion, worldwide spreading https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7834510/
VERY IMPORTANT (Showing vaccinated transfer of Abs to unvaccinated) – Evidence for Aerosol Transfer of SARS-CoV2-specific Humoral Immunity https://www.medrxiv.org/content/10.1101/2022.04.28.22274443v1
To evaluate this hypothesis, we obtained nasal swabs from children living in households in which parents or family members had varying degrees of SARS-CoV2-specifc immunity, including those unvaccinated, vaccinated and COVID-19+. Initial comparison of nasal swabs acquired from children living in vaccinated households revealed readily detectable SARS-CoV-2-specific IgG (Fig 1E), especially when compared to the complete deficit of SARS-CoV-2-specific antibody detected in the few nasal swabs we obtained from children in non-vaccinated households. We then used the variation in parents’ levels of intranasal IgG as the basis of stratification across all children’s samples. Log transformation of the data from thirty-four adult-child pairs established antibody cut-offs for high vs low parental intranasal antibody levels. Evaluation of samples in this fashion revealed that high intranasal IgG in vaccinated parents was significantly associated (p-value = 0.01) with a 0.38 increase in the log transformed intranasal IgG gMFIs within a child from the same household (Fig 1F).
IMPORTANT 2021 STUDY (Transmission in vaccinated) – COVID-19 Vaccines May Not Prevent Nasal SARS-CoV-2 Infection and Asymptomatic Transmission https://pubmed.ncbi.nlm.nih.gov/33320052/ Non paywall https://journals.sagepub.com/doi/full/10.1177/0194599820982633
The divergence in immune response between mucosal and systemic vaccination is derived from the fact that human mucosal surfaces contain a localized immune system composed largely of mucosa-associated lymphoid tissue, which contributes up to 80% of all immunocytes within the body. Given that it operates within a highly heterogenous and contaminated milieu, the mucosa-associated lymphoid tissue tends to be highly compartmentalized and, to some extent, functions independently of the systemic immune system. Consequently, following local antigen exposure, activated mucosal-derived B and T cells may only selectively populate the mucosa of origin through immunocyte and mucosa–specific receptor interactions. This site specificity of the mucosal immune response thereby significantly impedes the efficacy of systemic vaccination on local nasal respiratory mucosal immunity.
These concerns are amplified in light of multiple studies indicating that the nasal olfactory epithelium in particular is an early site of SARS-CoV-2 infection. Olfactory epithelium infection frequently manifests as a disturbance in the sense of smell and taste, which may be the only symptom in mild COVID-19 cases. Molecular and immunohistochemical studies demonstrate significantly higher levels of expression of the SARS-CoV-2 entry protein, ACE2, in olfactory sustentacular cells than even the respiratory epithelium.4 While the olfactory epithelium immune system is incompletely understood, it is conceivable that this primary neural tissue may also be relatively immune privileged and thus even further separated from the response to systemic vaccination than other airway mucosal surfaces. Unchecked by systemic humoral immune protection, SARS-CoV-2 entering the nasal airway may be able to infect and propagate there, shedding infectious virus asymptomatically for an unknown period of time.
IMPORTANT (Transmission is 53% chance of delveloping Covid even with a guaranteed level of exposure, not natural transmission) – Safety, tolerability and viral kinetics during SARS-CoV-2 human challenge in young adults https://www.nature.com/articles/s41591-022-01780-9
Authors found:
Thirty-six healthy volunteers aged 18–29 years were enrolled according to protocol-defined inclusion and exclusion criteria. [..] All participants were inoculated with 10 TCID50 of SARS-CoV-2/human/GBR/484861/2020 (a D614G-containing pre-alpha wild-type virus; GenBank accession number OM294022; TCID50 is the median tissue culture infectious dose) by intranasal drops (Fig. 1b). [..] Eighteen participants, 53% according to the per-protocol analysis (95% confidence interval (CI) (35, 70)), subsequently developed PCR-confirmed infection.
IMPORTANT (Transmission increased 6.2 times during Omicron despite high 93% vaccination rates) – SARS-CoV-2 Variants and Age-Dependent Infection Rates among Household and Nonhousehold Contacts https://wwwnc.cdc.gov/eid/article/29/8/22-1582_article
Household contacts have a 6.2 times higher chance of infection during the Omicron period of the COVID-19 pandemic when compared to the pre-VOC period. Children and adolescents were particularly vulnerable. But regardless of increasing non household contact among persons in the Prefecture aged 0-19 years, nonphysical contact and non-pharmacological control measures in school and daycare centers could have led to lower COVID-19 infection rates, with fewer large outbreaks in schools.
The Japanese team focusing on Toyama also found that for persons aged 60 years and above COVID-19 infection rates decreased during the Delta period, but again surged during the Omicron period, possibly due to waning vaccine impact plus the weakened effect of the Omicron VOC, despite vaccination rates of 93% among this cohort during the Omicron period.
The Japanese epidemiologists note that among the elderly, despite high vaccination rates, infectivity surged greater than other ages, likely because of close contact due to caregiving and nursing care scenarios. Importantly, Miyahara and colleagues write, “The value of protecting those who care for elderly case-patients should thus be emphasized.”
IMPORTANT (Vaccinated and unvaccinated similar viral loads) – Quantity of SARS-CoV-2 RNA copies exhaled per minute during natural breathing over the course of COVID-19 infection https://www.medrxiv.org/content/10.1101/2023.09.06.23295138v1.full-text
Vaccinated and unvaccinated individuals exhaled similar levels of SARS-CoV-2 RNA
Whether vaccinated individuals who experience breakthrough infection with COVID-19 shed lower levels of virus on breath is unknown. Our data set included 57 samples collected by 11 vaccinated participants with breakthrough infections (Table 1). We found that vaccinated and unvaccinated participants exhaled similar numbers of SARS-CoV-2 RNA copies (Fig 2C), when accounting for age, sex, presence of co-morbidities, days since symptom onset and symptom severity (Supplementary Appendix, Wilcoxon rank sum test, P = 0.31, z = 1.02) (Fig 3A). Viral RNA levels in 57 samples collected by vaccinated individuals on days 1 to 16 from symptom onset ranged from 0 to 549 exhaled copies per minute (%95 CI: [17, 78]) while viral loads for unvaccinated individuals on days 1 to 16 ranged from 0 to 876 exhaled copies per minute (%95 CI: [25, 55]).
IMPORTANT (Transmission vectors in household transmission of SARS-CoV-2) – Risk factors and vectors for SARS-CoV-2 household transmission: a prospective, longitudinal cohort study https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(23)00069-1/fulltext
VERY IMPORTANT (Transmission vectors) – Does COVID-19 Spread Through Droplets Alone? https://www.frontiersin.org/articles/10.3389/fpubh.2020.00163/full
VERY IMPORTANT (No difference in viral loads between vaccinated status) – No Significant Difference in Viral Load Between Vaccinated and Unvaccinated, Asymptomatic and Symptomatic Groups Infected with SARS-CoV-2 Delta Variant https://academic.oup.com/ofid/article/9/5/ofac135/6550312?login=false (Published title: Viral Load Among Vaccinated and Unvaccinated, Asymptomatic and Symptomatic Persons Infected With the SARS-CoV-2 Delta Variant) – MedRXIV submission https://www.medrxiv.org/content/10.1101/2021.09.28.21264262v1
VERY IMPORTANT (Viral load dynamics) – Viral load dynamics of SARS-CoV-2 Delta and Omicron variants following multiple vaccine doses and previous infection https://www.nature.com/articles/s41467-022-33096-0
Authors find: This study indicates that overall the presumed vaccination-related immunity to SARS-CoV-2 has only a negligible long term (>70-days) effect on Ct value, a common surrogate for VL and infectiousness. The combination of vaccine waning and vaccine evasion are most likely the drivers of this finding. In lieu of several prominent publications describing vaccine effectiveness in prevention morbidity and hospitalization for Omicron18,19,20, this study mandates reevaluating the role of current vaccination campaigns in harnessing the potential infectivity of COVID-19 at a time scale >2 months.
IMPORTANT (Mucosal immunity for Covid-19) – Mucosal Immunity in COVID-19: A Neglected but Critical Aspect of SARS-CoV-2 Infection https://pubmed.ncbi.nlm.nih.gov/33329607/
Authors found:
The mucosal immune system is the largest component of the entire immune system, having evolved to provide protection at the main sites of infectious threat: the mucosae. As SARS-CoV-2 initially infects the upper respiratory tract, its first interactions with the immune system must occur predominantly at the respiratory mucosal surfaces, during both inductive and effector phases of the response. However, almost all studies of the immune response in COVID-19 have focused exclusively on serum antibodies and systemic cell-mediated immunity including innate responses. This article proposes that there is a significant role for mucosal immunity and for secretory as well as circulating IgA antibodies in COVID-19, and that it is important to elucidate this in order to comprehend especially the asymptomatic and mild states of the infection, which appear to account for the majority of cases. Moreover, it is possible that mucosal immunity can be exploited for beneficial diagnostic, therapeutic, or prophylactic purposes.
IMPORTANT (Vaccinated 5X more contagious) – Duration of Shedding of Culturable Virus in SARS-CoV-2 Omicron (BA.1) Infection https://www.nejm.org/doi/full/10.1056/NEJMc2202092
The characteristics of the participants were similar in the two variant groups except that more participants with omicron infection had received a booster vaccine than had those with delta infection (35% vs. 3%) (Tables S1 and S2 in the Supplementary Appendix, available with the full text of this letter at NEJM.org). In an analysis in which a Cox proportional-hazards model that adjusted for age, sex, and vaccination status was used, the number of days from an initial positive polymerase-chain-reaction (PCR) assay to a negative PCR assay (adjusted hazard ratio, 0.61; 95% confidence interval [CI], 0.33 to 1.15) and the number of days from an initial positive PCR assay to culture conversion (adjusted hazard ratio, 0.77; 95% CI, 0.44 to 1.37) were similar in the two variant groups (Figure 1A through 1C and S1 through S3, and Tables S3 through S5). The median time from the initial positive PCR assay to culture conversion was 4 days (interquartile range, 3 to 5) in the delta group and 5 days (interquartile range, 3 to 9) in the omicron group; the median time from symptom onset or the initial positive PCR assay, whichever was earlier, to culture conversion was 6 days (interquartile range, 4 to 7) and 8 days (interquartile range, 5 to 10), respectively. There were no appreciable between-group differences in the time to PCR conversion or culture conversion according to vaccination status, although the sample size was quite small, which led to imprecision in the estimates (Figure 1D and 1E).
IMPORTANT (Humidity on transmission) – The dynamics of SARS-CoV-2 infectivity with changes in aerosol microenvironment https://www.pnas.org/doi/10.1073/pnas.2200109119
IMPORTANT – Imperfect Vaccination Can Enhance the Transmission of Highly Virulent Pathogens https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002198
IMPORTANT – SARS-CoV-2 Omicron VOC Transmission in Danish Households https://www.medrxiv.org/content/10.1101/2021.12.27.21268278v1.full
IMPORTANT (Transition from Delta to Omicron primarily driven by immune evasion, with 1.10 times higher odds of infection for unvaccinated, 2.38 times for fully vaccinated, and 3.20 times for booster-vaccinated) – Household transmission of the SARS-CoV-2 Omicron variant in Denmark https://www.nature.com/articles/s41467-022-33328-3
IMPORTANT (Omicron time to symptom onset median 3 days) – Outbreak caused by the SARS-CoV-2 Omicron variant in Norway, November to December 2021 https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2021.26.50.2101147
IMPORTANT () – Incident SARS-CoV-2 Infection among mRNA-Vaccinated and Unvaccinated Nursing Home Residents https://www.nejm.org/doi/full/10.1056/NEJMc2104849
Administration of covid-19 mRNA vaccine to Nursing Home patients did NOT lower total SARSCOV2 infections, barely lowered symptomatic infections (-0.39%), vs. unvaxxed, when analyzed appropriately, i.e., incl ALL infections!
1240/18,242 =6.8% with ANY incident SARS-CoV-2 infections among the vaccinated, & 270/3,990 also=6.8% incident SARSCOV2 infections among the unvaccinated by including infections which accrue days 0-14 Vaccinated with at least one dose=335/18,242=0.0184 → (1.84%) with SYMPTOMATIC incident SARS-CoV-2 infections among the vaccinated, & 90/3,990=0.0223 = (2.23%), a mere 0.39% absolute reduction, & a Number Needed to Vaccinate of 256 to prevent 1 SYMPTOMATIC SARS-CoV-2 infection
Supplementary Table S3
Nursing home staff vaccination rate showed NO association with resident infection rate. Yet despite this hospitals across the country fired unvaccinated nurses claiming they placed patients at risk.
IMPORTANT – Evolution of SARS-CoV-2 Shedding in Exhaled Breath Aerosols https://www.medrxiv.org/content/10.1101/2022.07.27.22278121v2 Published https://academic.oup.com/cid/article/76/5/786/6773834?login=false
SARS-CoV-2 Aerosol Shedding During Omicron (BA.1, BA.1.1, and BA.2) Infections
Among Omicron cases, we detected viral RNA in the EBA of 19 (66%) and 2 (both BA.1.1) yielded positive virus cultures from their fine EBA. One was fully vaccinated (not boosted) with BNT162b2 and emitted the highest number of viral RNA copies in a fine EBA sample (1.8 × 107) observed over the course of the pandemic. The other individual, fully vaccinated and boosted with BNT162b2, shed 2.9 × 103 viral RNA copies into fine EBA.
Fine EBA viral RNA loads from Omicron cases were, on average, similar to those from Alpha and Delta cases (Figure 2; Supplementary Figure 1). We did not observe a significant difference in viral aerosol shedding between Omicron BA.1, BA.1.1, and BA.2 (P > .05; Supplementary Figure 2).
Having received a vaccine booster was associated with shedding more viral RNA in coarse EBA (P = .0056; Supplementary Figure 5). However, boosters were not associated with fine (P = .97) or total EBA viral RNA load (P = .81; Supplementary Figure 5).
Five Omicron cases (1 BA.1, 1 BA.1.1, and 3 BA.2) were seropositive for anti-nucleocapsid (anti-N) IgG at enrollment, 1–6 days post–symptom onset. Four of the 5 had received a booster >8 days prior to symptom onset. Two reported prior infection(s), 2 denied prior infection, and 1 did not respond to questions about prior infection. We detected viral RNA in MTS samples from all 5. Their MTS, however, contained significantly fewer RNA copies than Omicron infections in the absence of anti-N IgG (P = .00045; Supplementary Figure 6). These 5 were the only Omicron cases that yielded culture-negative MTS samples (Figure 1). We detected viral RNA in saliva from only 1 of the 5, the nonboosted case, and that sample was culture negative. None of the 5 shed detectable levels of SARS-CoV-2 RNA in EBA.
IMPORTANT – The effect of variation of individual infectiousness on SARS-CoV-2 transmission in households https://www.medrxiv.org/content/10.1101/2022.08.30.22279377v1 Published https://elifesciences.org/articles/82611
IMPORTANT (Vaccinated naieve and unvaccinated no difference in transmission risk in households) – Reduced risk of SARS-CoV-2 infection among household contacts with recent vaccination and past COVID-19 infection: results from two multi-site case-ascertained household transmission studies https://www.medrxiv.org/content/10.1101/2023.10.20.23297317v1
Findings There were 1,532 contacts from 905 households included in this analysis. Of these, 67% were enrolled May–November 2022, when Omicron BA.4/5 predominated. Most contacts (89%) had some immunity to SARS-CoV-2 at the time of household exposure: 8% had immunity from prior infection alone, 51% from vaccination alone, and 29% had hybrid immunity. Sixty percent of contacts tested SARS-CoV-2-positive during follow-up. The risk of SARS-CoV-2 infection was not significantly reduced by vaccination but was reduced among those with prior infection considering such immunity separately (adjusted relative risk 0.83; 95% confidence interval: 0.77, 0.90); however, when accounting for both sources of immunity, only contacts with vaccination and prior infection had significantly reduced risk of infection (aRR: 0.81, 95% CI: 0.70, 0.93). The risk of infection was lower when the last immunizing event (vaccination or infection) occurred ≤6 months before COVID-19 affected the household (aRR: 0.69, 95% CI: 0.57, 0.83).
IMPORTANT – Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 https://www.nejm.org/doi/10.1056/NEJMc2004973?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed
IMPORTANT (IMMUNE PRESSURE) – Mechanisms of SARS-CoV-2 entry into cells https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8491763/
IMPORTANT – Increased airborne transmission of COVID-19 with new variants, Implications for health policies https://www.medrxiv.org/content/10.1101/2022.01.13.22269234v2 https://www.sciencedirect.com/science/article/pii/S0360132322003699?via%3Dihub
IMPORTANT – The Kinetics of COVID-19 Vaccine Response in a Community-Vaccinated Population https://www.jimmunol.org/content/early/2022/01/17/jimmunol.2100919
IMPORTANT – Vaccine effectiveness against SARS-CoV-2 transmission to household contacts during dominance of Delta variant (B.1.617.2), August-September 2021, the Netherlands https://www.medrxiv.org/content/10.1101/2021.10.14.21264959v1 Published https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2021.26.44.2100977
IMPORTANT – The role of airborne transmission in a large single source outbreak of SARS-CoV-2 in a Belgian nursing home in 2020 https://www.medrxiv.org/content/10.1101/2021.12.17.21267362v1
IMPORTANT – Mechanisms of SARS-CoV-2 Transmission and Pathogenesis https://www.cell.com/trends/immunology/fulltext/S1471-4906(20)30233-7
IMPORTANT (Viral load 251 times higher in vaccinated recipients with Delta)- Transmission of SARS-CoV-2 Delta Variant Among Vaccinated Healthcare Workers, Vietnam https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3897733
Authors found:
Findings: Between 11th–25th June 2021 (week 7–8 after dose 2), 69 healthcare workers were tested positive for SARS-CoV-2. 62 participated in the clinical study. 49 were (pre)symptomatic with one requiring oxygen supplementation. All recovered uneventfully. 23 complete-genome sequences were obtained. They all belonged to the Delta variant, and were phylogenetically distinct from the contemporary Delta variant sequences obtained from community transmission cases, suggestive of ongoing transmission between the workers. Viral loads of breakthrough Delta variant infection cases were 251 times higher than those of cases infected with old strains detected between March-April 2020. Time from diagnosis to PCR negative was 8–33 days (median: 21). Neutralizing antibody levels after vaccination and at diagnosis of the cases were lower than those in the matched uninfected controls. There was no correlation between vaccine-induced neutralizing antibody levels and viral loads or the development of symptoms.
IMPORTANT – Impact of Delta and Vaccination on SARS-CoV-2 transmission risk: Lessons for Emerging Breakthrough infections https://www.medrxiv.org/content/10.1101/2022.03.02.22271385v1
IMPORTANT – Effect of Vaccination on Household Transmission of SARS-CoV-2 Delta VOC https://www.medrxiv.org/content/10.1101/2022.01.06.22268841v1
IMPORTANT – Community transmission and viral load kinetics of the SARS-CoV-2 delta (B.1.617.2) variant in vaccinated and unvaccinated individuals in the UK: a prospective, longitudinal, cohort study https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(21)00648-4/fulltext
For all variant vaccination groups, the variation between participants seen in viral load kinetic parameter estimates was substantially larger than the variation in mean parameters estimated between groups. The modest scale of differences in viral kinetics between fully vaccinated and unvaccinated individuals with delta infection might explain the relatively high rates of transmission seen from vaccinated delta index cases in our study. We found no evidence of lower SARs from fully vaccinated delta index cases than from unvaccinated ones. However, given that index cases were identified through routine symptomatic surveillance, there might have been a selection bias towards identifying untypically symptomatic vaccine breakthrough index cases
IMPORTANT – Risk of SARS-CoV-2 transmission from newly-infected individuals with documented previous infection or vaccination https://www.ecdc.europa.eu/sites/default/files/documents/Risk-of-transmission-and-reinfection-of-SARS-CoV-2-following-vaccination.pdf
IMPORTANT (CASE STUDY) – Case Report: Sars-CoV-2 Infection in a Vaccinated Individual: Evaluation of the Immunological Profile and Virus Transmission Risk https://pubmed.ncbi.nlm.nih.gov/34249017/
IMPORTANT – Shedding of Infectious SARS-CoV-2 Despite Vaccination when the Delta Variant is Prevalent – Wisconsin, July 2021 https://www.medrxiv.org/content/10.1101/2021.07.31.21261387v6
Social distancing research:
IMPORTANT (Effects of social distancing on transmission) – Exploration of the effectiveness of social distancing on respiratory pathogen transmission implicates environmental contributions https://pubmed.ncbi.nlm.nih.gov/18823270/
Results: The odds ratio (OR) associated with FRI in closed units, compared with open units, was 1.13 (95% confidence interval [CI], 0.99-1.28). The OR in units with a population greater than the median size, compared with units with a population lower than the median size was 1.38 (95% CI, 1.23-1.55). Between 5% and 9% of surface samples obtained from selected units harbored viable adenovirus.
Conclusions: FRI rates were not reduced in units that were closed to potentially contagious individuals. These findings imply that the primary source of the pathogen is likely environmental rather than human, and they underscore what is known about other virus types. Diligence in identifying the relative roles of different transmission routes is suggested for civilian settings similar to those described in the current study.
IMPORTANT (Virus spread airborne more than 2 metre distance communicated, so ineffective) – A numerical assessment of social distancing of preventing airborne transmission of COVID-19 during different breathing and coughing processes https://www.nature.com/articles/s41598-021-88645-2
It was found that particles can move up to 5 m with a decrease in concentration in the direction of the air flow. The conclusions made in this work show that, given the environmental conditions, the two meter social distance recommended by WHO is insufficient.
Evidence for Aerosol Transfer of SARS-CoV2-specific Humoral Immunity https://www.medrxiv.org/content/10.1101/2022.04.28.22274443v1
Transmission of SARS-CoV-2 by children to contacts in schools and households: a prospective cohort and environmental sampling study in London https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(22)00124-0/fulltext
Nasal Gene Expression of Angiotensin-Converting Enzyme 2 in Children and Adults https://jamanetwork.com/journals/jama/fullarticle/2766524
Nasal ACE2 Levels and COVID-19 in Children https://jamanetwork.com/journals/jama/fullarticle/2766522
Saliva is superior over nasopharyngeal swab for detecting SARS-CoV2 in COVID-19 patients https://www.nature.com/articles/s41598-021-02097-2#:~:text=In%20conclusion%2C%20saliva%20has%20higher,to%20diagnose%20COVID%2D19%20patients.
Indoor versus outdoor transmission of SARS-COV-2: environmental factors in virus spread and underestimated sources of risk https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7873670/
Modelling airborne transmission of SARS-CoV-2 using CARA: Risk assessment for enclosed spaces https://www.medrxiv.org/content/10.1101/2021.10.14.21264988v1
COVID-19 Vaccines May Not Prevent Nasal SARS-CoV-2 Infection and Asymptomatic Transmission https://pubmed.ncbi.nlm.nih.gov/33320052/
Coronavirus transmission among vaccinated people could raise the risk of an even more dangerous variant https://www.businessinsider.com/covid-transmission-vaccinated-people-risk-of-resistant-variant-2021-7?op=1&r=US&IR=T
Reducing risks from coronavirus transmission in the home—the role of viral load https://www.bmj.com/content/369/bmj.m1728
The epidemiological relevance of the COVID-19-vaccinated population is increasing https://www.thelancet.com/journals/lanepe/article/PIIS2666-7762(21)00258-1/fulltext?s=08
The Dynamics of SARS-CoV-2 Infectivity with Changes in Aerosol Microenvironment https://www.medrxiv.org/content/10.1101/2022.01.08.22268944v1
UK NIHR Bombshell: Fully Vaccinated Serve as Vectors, Comparable Transmission to Household Contacts https://www.trialsitenews.com/a/uk-nihr-bombshell-fully-vaccinated-serve-as-vectors-comparable-transmission-to-household-contacts
Vaccinated People Easily Transmit COVID-19 Delta Variant in Households: UK Study https://www.theepochtimes.com/vaccinated-people-easily-transmit-covid-19-delta-variant-in-households-uk-study_4074277.html
Large UK Observational Study: COVID-19 Vaccines Don’t Stop Transmission for Long—Rethinking the Vaccination to Herd Immunity Premise https://www.trialsitenews.com/a/large-uk-observational-study-covid-19-vaccines-dont-stop-transmission-for-long-rethink-the-vaccination-to-herd-immunity-premise
SARS-CoV-2 Aerosol Transmission Indoors: A Closer Look at Viral Load, Infectivity, the Effectiveness of Preventive Measures and a Simple Approach for Practical Recommendations https://www.medrxiv.org/content/10.1101/2021.11.04.21265910v1
What is the vaccine effect on reducing transmission in the context of the SARS-CoV-2 delta variant? https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(21)00690-3/fulltext