Initial report of decreased SARS-CoV-2 viral load after inoculation with the BNT162b2 vaccine

Abstract

Beyond their substantial protection of individual vaccinees, coronavirus disease 2019 (COVID-19) vaccines might reduce viral load in breakthrough infection and thereby further suppress onward transmission. In this analysis of a real-world dataset of positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test results after inoculation with the BNT162b2 messenger RNA vaccine, we found that the viral load was substantially reduced for infections occurring 12-37 d after the first dose of vaccine. These reduced viral loads hint at a potentially lower infectiousness, further contributing to vaccine effect on virus spread.The recently authorized BNT162b2 Coronavirus Disease 2019 (COVID-19) messenger RNA (mRNA) vaccine is approximately 95% efficient in preventing polymerase chain reaction (PCR)-confirmed symptomatic disease from 7 d after the second dose and also provides some early protection starting 12 d after the first dose 1,2 . As countries race to vaccinate a substantial portion of their populations in the coming months, it is hoped that the basic reproduction number of the virus will decrease. This effect can be achieved by reducing the number of susceptible people, as well as by reducing viral load and, thereby, viral shedding of post-vaccination infections, which might render them less infectious [3][4][5][6][7] . However, the effect of vaccination on viral load in COVID-19 post-vaccination infections is currently unknown 8 .As of February 11, 2021, Maccabi Healthcare Services (MHS) in Israel has vaccinated more than 1 million of its members as part of a national rapid rollout of the vaccine. MHS member SARS-CoV-2 tests are often carried out in the MHS central laboratory, which offers the opportunity to track post-vaccination infections. In this study, we retrospectively collected and analyzed the quantitative reverse transcription PCR (RT-qPCR) test measurements of three SARS-CoV-2 genes-E, N and RdRp (Allplex 2019-nCoV assay, Seegene)-from positive post-vaccination tests performed at the MHS central laboratory between December 21, 2020, and February 11, 2021 (n = 4,938 patients, study population; Table 1). The study period was characterized by high and steady rates of positive COVID-19 tests (Extended Data Fig. 1), indicating an ongoing epidemic wave.In an analysis of the infection cycle threshold (Ct) over time, we found that the mean viral load substantially decreased 12 d after vaccination with the first vaccine dose, coinciding with the known early onset of vaccine-mediated protection 1 . When we calculated the mean Ct for post-vaccination infections identified on each day

Allocation of COVID-19 vaccination: when public prioritisation preferences differ from official regulations

“…While vaccinating the vulnerable primarily reduces morbidity and mortality, the immunisation of medical personnel not only protects those persons from infection, but also sustains the medical infrastructures necessary to control the pandemic. Furthermore, as recent research suggests that vaccination limits transmission of the coronavirus, 14 vaccinating medical personal with many contacts is likely to protect much more people than vaccinating the vulnerable. Participants may also have assumed that vaccinating a 50-year-old doctor saves more life years than vaccinating someone 80 years or older.…”

Quantifying the relationship between SARS-CoV-2 viral load and infectiousness

“…Conversely, we studied the effects of lower levels of viral load, as expected from a partial protection conferred by vaccination. Epidemiological studies in Israel reported a 3-5-fold lower viral load in infected vaccinated individuals as compared to unvaccinated individuals 4 .…”

“…First, we increased the viral production parameter, , by a factor of 2, 4, 8,16, 32, 64 and 100 corresponding to observed increases of 1-7 value for different variants 2,10,11 . Second, we decreased the production parameters by a factor of 2, 4, 8 and 16 as well 4 to emulate the impact of vaccination 4,13 . Simulations were performed following same procedure as above.…”

“…In the context of variants of concern 2,3 , that are likely associated with larger viral loads, it becomes even more critical to delineate the contribution of viral shedding from other suspected factors associated with an increased transmission. Further, as antiviral and vaccine strategies are being implemented, that directly reduce the amount of viral shedding 4 , it is essential to understand how they may contribute to a reduction in SARS-CoV-2 transmission.…”

A SARS CoV-2 nucleocapsid vaccine protects against distal viral dissemination

“…These vaccines have shown high efficacy against severe disease and death, but they do not always confer sterilizing immunity 1–6 . In particular, breakthrough infections can be detected in nasopharyngeal swabs of vaccinated individuals 7–9 . Nasopharyngeal swabs typically contain viruses derived from the proximal site of challenge (the respiratory system), which may not reflect ongoing virus replication at distal sites of the body.…”