To quote President Biden, “This is not March of 2020… we know more.” It’s been nearly two years since we first dedicated an EBM Focus to COVID with COVID-19: Ten Things You Need to Know. Reflecting on the questions we asked in that first edition, “Is ibuprofen safe to use during COVID-19 infection?”, and even questions in the second article, Ten Things You Need to Know NOW, “Are supplements helpful in preventing COVID-19 infection or reducing severity?”, it’s clear that we really have come a long way. We are entering the third year of the COVID-19 pandemic with vaccines, treatments, and yes, new variants. In the spirit of evidence-informed decision making and squashing misinformation, allow us to present the 2022 edition of Ten Things You Need to Know Now.
1. How contagious is Omicron?
Two to three times as contagious as Delta. In a world ready to realize an endgame for this pandemic, this new variant has raised concerns about increased transmissibility and decreased vaccine efficacy (not to mention the uncertainty over how to pronounce its name). Omicron has dozens of mutations in the spike protein, the target of monoclonal antibodies and existing vaccines. Researchers postulate the mutations occurred in a single immunocompromised host over a period of about 10 months, rather than a single strain that accumulated the mutations over subsequent transmissions. Early studies from households and contacts (unadjusted for prior vaccination or infection) show that 19 percent of Omicron index cases resulted in a secondary household case compared to eight percent with Delta (adjusted odds ratio 3.2 [95%CI 2.0-5.0, p <0.001]). Oh, and apparently it’s equally acceptable to pronounce it “AH-muh-kraan” or “OH-muh-kraan”.
2. Are vaccines still effective against Omicron?
Yes — if you are boosted after a primary vaccine series. An early non-peer reviewed case-control study of vaccine effectiveness in 581 people with Omicron demonstrated 70-75 percent effectiveness against symptomatic infection in boosted patients compared to only 30 percent in those who had only completed a primary (2-dose) vaccine course. Importantly however, two doses of the Pfizer vaccine still provided 70 percent protection against severe disease requiring hospitalization. Patients studied had completed either a Pfizer or AstraZeneca primary vaccine series, but all booster doses were Pfizer. While overall vaccine effectiveness against Omicron appears to be significantly lower than effectiveness against Delta based on these early data, 75 percent is still considered a “moderate to high” vaccine effectiveness so we should still be trying to get as many people boosted as possible. Lab data from Moderna and Johnson & Johnson report similar news about effectiveness against Omicron, but clinical reports are still pending for those vaccines.
3. Should we recommend mix-and-match boosting?
Maybe. While it is now clear that none of the vaccines provide lifelong immunity against all COVID variants, mRNA vaccines may be more nimble to produce and potentially more efficacious in the long run. One interesting pragmatic world-wide experiment happening now is the large number of people initially vaccinated with one vaccine but boosted with another. Epidemiologists call this “heterologous mixing” of vaccines. Theoretical benefits may include exposure to different antigens or activation of different parts of the immune system, while harms might include different potential side effects and lack of clarity in public health messaging. Mixing is happening out of necessity in some settings, but also as part of clinical trials. Initial results coming in seem to favor heterologous boosting, but we need more long-term data to make any conclusions.
4. Can you give flu and COVID vaccines together?
Yes, definitely. Initially, the CDC recommended spacing flu and COVID-19 vaccines by at least 14 days due to lack of data and to prevent false attribution of side-effects to COVID-19 vaccines, but evidence now supports concomitant vaccination as standard practice. A multicentered randomized trial in the UK evaluated concomitant administration of two COVID-19 vaccines (Pfizer and AstraZeneca) with three inactivated influenza vaccines. Results from participant diaries showed that systemic reactions were similarly common between groups. Immune response (as measured by SARS-CoV-2 spike protein antibody and hemagglutinin antibody inhibition) to both COVID-19 and influenza vaccination, respectively, was preserved. The bottom line is that concomitant administration of COVID-19 and influenza vaccines produced similar side effects without altering immune response and not only protects against infection but reduces the burden on the healthcare system.
5. Should COVID-19 vaccination be given during pregnancy?
Yes. Numerous organizations including the CDC and American College of Obstetricians and Gynecologists (ACOG) currently recommend COVID-19 vaccination, including booster doses, for pregnant and lactating individuals. From cohort studies, it appears vaccines are safe and effective in preventing infection.
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