By Tuesday, the pre-prints are picking up, so a few interesting studies today.
This paper assessed whether the timing of mitigation of spread actions has an impact on cases. (Medrxiv Paper) The study analyzed 87 interventions across 17 countries for their impact on mortality rates. They authors also conducted a literature review. They found no association between the initiation of an intervention and mortality rates. In particular, being faster in implementing a measure after the Chinese came clean, or the country first experienced a case or a death, had no association with the country’s mortality rate. These results rebut the notion that earlier implementation of mitigation measures would lower cases or deaths. Of course that is likely because these measures are futile.
We are continuing to see more papers finding that there is a long-lasting extensive adaptive response to CV-19 infection. Here are two new papers in this area. In the first, T cell response was probed for up to 9 months post infection in 32 Chinese patients. (Medrxiv Paper) A few patients showed signs of some decline in response and they tended to have had asymptomatic infections. People who showed some antibody decline were less likely to have a T cell response that stayed stable. In the second paper, 185 patients were followed for up to 6 months. Antibodies were relatively stable, memory B cells actually increased. T cells showed a more variable course, declining in some patients. Overall, my takeaway from this body of research is that we can assume that infected people have an adequate and lasting immune response to fend off re-infection.
Another paper that examines the relationship between viral load and severity of disease. (Medrxiv Paper) 448 Spanish patients were used in the study. Nasal swabs were used to collect samples for PCR tests. Lower cycle numbers were clearly associated with more severe disease. So it is important that this metric be reported with the test results.
An updated version of the Gomes paper using a model that includes more heterogeneity in infectiousness and susceptibility in a population. (Medrxiv Paper) The paper continues to find that transmission may slow substantially at relatively low levels of infection in the population.
This is another in the line of studies suggesting that some vaccinations may offer protection agains CV-19. (DTP Study) The authors checked a number of vaccines and pathogens to see if they contained sequence fragments similar to CV-19. Most did not and therefore were unlikely to offer cross-reactive protection. The Diphtheria, Tetanus and Pertussis vaccine, however, did show significant cross-reactive potential and stimulation of T and B cell responses. Almost all children receive this vaccine, which may be a factor in their lower risk.
And for those who like to have lots to worry about, this study checked the persistence of CV-19 on fresh produce. (Medrxiv Paper) A seasonal coronavirus was used, not CV-19. In general the virus was gone with 24 hours after being placed on the produce item. But cucumber retained it for up to 3 days.