Many vaccines require more than one dose to be effective in preventing disease, and Covid-19 is no exception. That’s according to Jonathan Zenilman, an infectious disease expert at Johns Hopkins.

Zenilman: We do know that the boosts, actually at several different dosing levels, provide exponential increases in antibody levels. The framework is are these really boosters or is the true schedule of the vaccine something that should be 0,1, and six months, very similar to other vaccines that we use. And actually was the problem that because of the pandemic they really needed accelerated schedules?  :28

Zenilman says that as global criticism mounts against providing third doses on a routine basis when so many people haven’t had even one dose, it’s worth considering that the best protection against Covid-19 may very well be a three or more dose regimen. At Johns Hopkins, I’m Elizabeth Tracey.


Antibodies are proteins that circulate in the blood and act as first responders to viruses, hopefully warding off infection. Antibodies are produced either in response to immunization or natural infection, but whether they provide a useful measure of protection is unclear. That’s according to Stuart Ray, an infectious disease expert at Johns Hopkins.

Ray: There’s the formal question of whether the antibodies measure the thing that we’re trying to detect. The other is whether there’s a correlation that’s useful, and whether we can identify people at risk in a reliable way. Neutralizing antibody assays can measure something but we don’t know exactly where the threshold is for protection. We can try to make some inferences but even that estimate, with the best estimates we have, is imperfect. But both because we don’t exactly know what level and we’re only measuring one particular function, there’s lots of reasons why there’s uncertainty.  :29

Ray says attempts to use neutralizing antibody levels against Covid-19 are a case in point for this uncertainty. At Johns Hopkins, I’m Elizabeth Tracey.


The EU and many other high income countries are turning increasingly toward booster shots for Covid-19, at least for some groups of people. Mark Sulkowski, an infectious disease expert at Johns Hopkins, explains some of the data.

Sulkowski: Israel was a country was there was a high and early uptake in vaccine in nearly 80% of adults were vaccinated. The delta variant emerged and there was a high case rate and hospitalization rate among vaccinated individuals. That prompted a third dose for persons 60 or older greater than or equal to five months since full vaccination. On Med Archive is this report, suggesting the estimated what they called ‘booster protection’ for individuals who received a third dose. The end of this was in August so it wasn’t a long period of follow up time. And this study has generated a lot of controversy.  :35

Sulkowski says the controversy stems from the short follow up time and notes that much of the world’s population still doesn’t have a first dose even as others are now moving to third shots. At Johns Hopkins, I’m Elizabeth Tracey.


In this next podcast, Elizabeth Scala and Holley Farley discuss how to put together a podium presentation. Holley offers tips related to how to verbally present information, the use of large font size, use graphics, and engage the audience. Holley mentions the use of an abstract outline, saving the abstract in word with headers, and utilizing it as your podium presentation template. Finally, they encourage listeners to view past podium presentations, attend CNI’s annual workshop on dissemination, and provide handouts.


Studies conducted over the last several months are bearing fruit as Covid vaccines for children appear close to deployment. Emergency use authorizations are expected from the FDA soon, with many parents anxious to have their children immunized. Jonathan Zenilman, an infectious disease expert at Johns Hopkins, describes the process.

Zenilman: There’s two groups of kids. One is five to twelve and the other is six months to under five. The trials to look at kids did not look at efficacy, the FDA allows something called bridging, and what they needed to do was show safety and dose range. The major issue with kids has been fevers, and we’ve seen this with the adolescents too but it’s playing out in kids as well. They have really good immune systems and they react to these things. Fevers in kids occur but they tend to be easily controlled.  :31

Zenilman says over the counter medicines can help. At Johns Hopkins, I’m Elizabeth Tracey.


Shedding virus is the term used to describe the state of being infectious to others, and with Covid-19 there’s a lot about this state we still don’t know. Anna Durbin, an infectious disease expert at Johns Hopkins, says the picture is even more complicated when someone who is vaccinated becomes infected.

Durbin: This is viral load by PCR and we don’t know how much of it is infectious. So that’s my first caveat. We could be measuring dead virus or virus bound to antibody but by and large the more virus you have the more likely you are to transmit, the more likely you are to be symptomatic which can lead to cough and other things that also improve transmission. And generally it could be also that you harbor the virus longer so I think there are several different factors and included in that is behavioral.  :31

Durbin says it is known that people who’ve been vaccinated generally experience less severe cases of Covid-19 but that they can infect others, but how long that period lasts is still being investigated, so for now, masks and physical distancing remain good ideas. At Johns Hopkins, I’m Elizabeth Tracey.


Researchers around the world are sequencing new variants of Sars-CoV2 as they emerge, but while it may be possible to pinpoint changes in the virus it’s not known what those changes might portend. That’s according to Stuart Ray, an infectious disease expert at Johns Hopkins.

Ray: Here I am noting that delta lacks those changes in most of the sequences, so while we thought 501, 44 were super important, this virus continues to surprise us, and delta has other features. So what we thought was important before may not be important now, and I think this is important as we think about where the next variant might come from. They keep on coming out of left field and so we have to be humble about our ability to predict what’s going to be dominant six months from now if we’re designing a new antigen for a vaccine for instance.  :29

Ray says that current vaccines are holding their own against all important variants of Sars-CoV2, dramatically reducing both hospitalizations and deaths related to infection. At Johns Hopkins, I’m Elizabeth Tracey.