Coronavirus: So you’re what?

We’re getting closer and closer to reaching herd immunity – but shouldn’t jump the gun.

A health worker draws a dose of the AstraZeneca's coronavirus disease (COVID-19) vaccine, at the vaccination center in the Newcastle Eagles Community Arena, in Newcastle upon Tyne, Britain, January 30, 2021. (photo credit: REUTERS/LEE SMITH)
A health worker draws a dose of the AstraZeneca's coronavirus disease (COVID-19) vaccine, at the vaccination center in the Newcastle Eagles Community Arena, in Newcastle upon Tyne, Britain, January 30, 2021.
(photo credit: REUTERS/LEE SMITH)
Mazal tov on getting vaccinated! We are confident you have made the right decision, and most Israelis are as well. Israel is leading the world’s vaccine rollout by a landslide, with 115 doses administered per 100 people as of March 30, 2021 (full coverage would be close to 200 doses per 100 people). Only the UAE and the US, also front-runners, have come close, at 84 and 44 doses per 100 people respectively, according to The New York Times Coronavirus Vaccine Tracker.
As a rapidly-increasing number of people get their shot, we see a population divided, into the vax-ed and the vaxed-nots, and etiquette starts to get a little sticky. Don’t worry, an epidemiologist and a biomedical scientist are here to clear up the confusion. 
To mask or not to mask? That is the question
Do you finally invite Aunt Margalit to your Lag Ba’Omer Bonfire? How about your Shabbat table? Is it okay to take public transportation? Should you still wear a mask and social distance? The answer is, yes – for now. We don’t yet have enough data to determine whether vaccinated people can spread COVID-19 to unvaccinated people, although preliminary studies seem to point to a very low probability of transmission if the unvaccinated people are healthy and low risk, but it’s still best to err on the side of caution. 
According to the CDC, vaccinated people may behave normally in settings with other vaccinated people but should be cautious around the unvaccinated and in public – mask up, stay 6 ft (2 m) away, and use hand sanitizer. Allowances may be taken at small gatherings with just one other household provided all members of that household are low risk, meaning persons under 65 who are neither immunosuppressed nor have any pre-existing conditions relating to cardiovascular, lung, or immune function. High-risk conditions may also include pregnancy, heart disease, stroke, cancer, COPD, diabetes, cystic fibrosis, Alzheimer’s, Down’s Syndrome, HIV, and others. [Interim Public Health Recommendations for Fully Vaccinated People | CDC] 
Vaccinated people should still avoid large gatherings but can take public transportation if masked and maintaining social distance. Going to a Lag Ba’Omer bonfire with your vaccinated parents, unvaccinated sister with her unvaccinated husband and kids should be fine, since only one household has not yet been vaccinated. Going to your vaccinated, older, high-risk parents’ house for Shabbat is perfectly fine, if all involved are vaccinated. If your shul is hosting a dinner party at the rabbi’s house, it might not be the wisest choice to attend, since you don’t know the vaccination status of all the guests. 
What about variants?
It’s not surprising that many variants of COVID-19 have developed over the last year. Viral genomes are notoriously mutable because they lack the DNA or RNA-editing enzymes of normal cells. Mutations are also a numbers game: the more people that catch COVID-19, the more transmission events and chances for mutations. A typical COVID-19 virus accumulates around two mutations per month – multiply that by the millions of cases worldwide, and the thousands of variants identified by scientists become understandable. 
The variants that we really need to be alert for are those that make a significant structural change in one of the viral components, like the spike protein, since that is what most vaccines target. So far, the current vaccines seem to be protective against these emerging variants. However, some of the variants do interact differently with certain vaccines, which may leave people more susceptible or at a higher-risk of developing complications of COVID-19 with or without a vaccine. Some variants including the UK variant have also been shown to result in a worse prognosis more often, which highlights the importance of exercising caution even once vaccinated. 
The beginning of the end of the pandemic?
As more data emerges and more people get vaccinated, we get closer and closer to reaching herd immunity, but we shouldn’t jump the gun. First, since herd immunity for COVID-19 has never actually been reached before, scientists aren’t entirely sure what percentage of people need to be immune for a society to achieve herd immunity in practice. Israel, with its light-speed vaccination drive, will likely be the first country to test this in practice, but the Israeli vaccination experiment will still remain vulnerable to variants for the foreseeable future, underscoring the need for a strong global vaccination campaign.
Second, none of the current COVID vaccines are 100% effective (although Pfizer and Moderna come close, and while efficacy is one important measurement of vaccine effectiveness, so is percentage of already-vaccinated serious/hospitalized persons with COVID-19, which is extremely low). This suggests that there will always be a small minority of vaccinated people for whom immunity never takes full effect. Finally, in countries like Iceland, where there are sometimes more tourists than residents, if the local population reaches herd immunity yet most tourists are unvaccinated, herd immunity would be harder to achieve.
As a result of these caveats, we may need a buffer on top of the minimum recommended herd immunity. Global health agencies like the WHO, CDC and the Israeli Ministry of Health will likely – or at least, they should – proceed with caution in recommendations for reopening. The United States should serve as a warning: Many counties have prematurely let their guard down due to vaccination rollout, and we are seeing additional waves of COVID-19 infections across the country. The key is to encourage your friends to get vaccinated too – the more people get vaccinated, the closer we get to herd immunity, and the sooner our lives – and our economies – may return to normal. 
Alexandra Markus Hutz, an adjunct professor of biomedical sciences at Shelem College, has a Master of Science from Columbia University and a Master of Public Health from Hebrew University of Jerusalem. She has worked as a biomedical scientist researching the impact of vitamin D on tuberculosis infection and progression, and as an assistant epidemiologist at the Health Ministry. She is passionate about promoting scientific and health literacy in the wider community.
Jamie Magrill is currently completing his Master of Science in Biomedical Sciences at Hebrew University. He has conducted research in the fields of cancer, diabetes and pathology for the past five years and co-authored scientific journal articles in publications like Cell Metabolism, Annals of Oncology and The Journal of Pathology. He has worked in science outreach as an educator, workshop facilitator and lecturer since 2017.