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How Effective Are Vaccines Against the Delta Variant? Should We Get Booster Shots? And Other Questions Answered

Infectious diseases physician and Chair of the Jefferson COVID-19 Task Force Dr. John Zurlo discusses everything from masking up (even when you’re fully vaccinated) to the potential of booster shots.

Infectious diseases physician Dr. John Zurlo has been a point person for COVID-19 since the early stages of the pandemic. He has served as the Chair of the Jefferson COVID-19 Task Force. He too felt the relief that so many others did when cases dipped early this summer, wondering if we had seen the worst of COVID. However, as cases again begin to spike across the country and in the Philadelphia region, as well as the introduction of the Delta variant, Dr. Zurlo is referring to this new chapter of the pandemic as “Chapter XXX,” because we still do not know how many other chapters lie ahead.

If you’re struggling to keep up with information these days, you’re not alone. Recommendations on masking have changed yet again but the push for vaccination remains. “It is the single most important thing you can do to keep yourself and your community safe,” says Dr. Zurlo. For those who are fully vaccinated, worries are emerging as some have had breakthrough infections.

Here, we turn to Dr. Zurlo for what he knows about the Delta variant, if and how much we should be adjusting our lifestyles to stay safe, and if boosters will be recommended in the near future.

You have been fully vaccinated since January 2021. Do you still wear a mask in public?

I don’t know whether people are vaccinated or not in these environments and we are all safer if everyone wears them. So yes, if I’m going to any indoor spaces like the grocery stores, I’m wearing a mask.

From a public health perspective, there are people in our community who are immunocompromised and may not respond to the vaccine. In older populations, vaccines also may not work as well. It is for these people that I wear a mask while in public settings and believe that everyone should. Remember that facemasks work best at preventing you from infecting someone else. We do not know how effective vaccination is in completely preventing infection. There is a chance that a vaccinated person can develop a mild infection and spread it.

Dr. John Zurlo standing in front of Thomas Jefferson University Hospital
Dr. John Zurlo standing in front of Thomas Jefferson University Hospital.

Do you agree then with the CDC’s recommendation to mask up in indoor public settings?

I agree with the recommendation. It’s a reasonable precaution. I do want to point out, however, that this is not as easy in a restaurant, where, of course, you are unmasked to eat. That’s a challenge. We have not seen a major surge in cases in our region but the numbers are climbing. In parts of the city with low vaccination rates, we would expect to see an increasing number of cases.  And so this masking recommendation makes sense.

I have taken a mask in my pocket with me wherever I go since the start of the pandemic. This is almost the best time if you think about it for Philadelphia to mask up because we’re not seeing a massive increase in cases. With masking, we can hopefully prevent a major surge in cases.

[Editor’s Note: For more expert tips on staying safe this summer, click here.]

Has there been a significant uptick in cases since the Delta variant presented in our region?

The Delta variant is clearly more transmissible and contagious. We have been mapping the number of cases all the way back to the beginning of the pandemic. We are now seeing case numbers rise since mid-July in both New Jersey and Pennsylvania. We are still seeing relatively small numbers of new hospital admissions on a daily basis but the numbers are slowly rising. We don’t want to go back to where we were in December and January when we were admitting nearly 100 patients per day.

How effective are the COVID-19 vaccines against Delta?

Data shows a very distinct correlation between low vaccination rates and high hospitalization rates. The vast majority of hospitalizations we are seeing across the country during this Delta surge are among unvaccinated individuals. This is however a developing story. There’s a much-referenced Israeli study that looked at the Pfizer vaccine and they noted declining effectiveness of the vaccine against Delta. They found it 39% effective in preventing symptomatic infection. But what they did note was that the vaccination was 88% effective in preventing hospitalization and 91% effective in preventing severe disease. This study was criticized because it only sampled some hundreds of patients.

There’s a more recent study from the United Kingdom that was published in the New England Journal of Medicine, looking at 19,000 patients with symptomatic infection. They compared infections caused by the Alpha variant, also known as the UK variant, which we saw in our surge in the spring both in Philadelphia and across the country, to the Delta variant, which took hold in the UK several weeks earlier than the U.S. The researchers looked at vaccinations that included the Pfizer vaccine and the AstraZeneca vaccine, which is not available here in the United States. The Pfizer vaccine showed 94% effectiveness for the Alpha variant and 88% for the Delta variant and slightly lower numbers for the AstraZeneca vaccine. So this study suggested a high rate of protection from this Delta strain. All studies of vaccination and the Delta variant have shown that they are very effective in preventing severe COVID infection.

I will also add we have reason to believe that Moderna is also effective, according to a briefing by Dr. Jay Butler from the Infectious Diseases Society of America in mid-July. They reported that 97% of newly reported cases with serious infection are among unvaccinated individuals.

Should you get a booster shot if you are already fully vaccinated?

Booster shots may be a reality for immunocompromised individuals and older populations in the near future. The challenge is that there are many kinds of immunocompromised patients, including bone marrow transplant patients, cancer patients and patients receiving immunosuppressive medications to treat autoimmune diseases like lupus. We do know that the vaccines are not as effective in many of these patient populations and in some elderly patients, who we know don’t respond as well as younger populations to many kinds of vaccines.

There may be a rationale for distributing boosters to individuals to prevent infection from variants like the Delta variant.

As for the general population, it is quite conceivable that we’ll find that over time, the effectiveness of vaccine wanes in all of us and we may need vaccine boosters, perhaps once more in a year or two, perhaps every few years. That is yet to be determined. There may be a rationale for distributing boosters to individuals to prevent infection from variants like the Delta variant. At this point in time, there is no clear guidance on the need for boosters, but this is once again, as everything with COVID, a developing story.

Should travel plans be postponed right now?

Personally, I probably wouldn’t make any plans to travel right now to areas of high COVID transmission, especially with what we’re seeing in many southern states. Places like Jacksonville, Florida are seeing higher hospitalization rates than what they were seeing in December/January.

If you have to travel, be super careful and wear a mask. Otherwise, don’t put yourself at risk—even though we believe that the risk of getting very sick with COVID-19 is very small when you’re fully vaccinated.

Should you get tested if you are vaccinated and start to have respiratory symptoms?

I think you should get tested. If you are a part of a high-risk group, you could qualify for monoclonal antibody infusion, which we believe reduces the severity of infection. And even if you’re not in that high-risk group, it’s important to get tested for the people around you. In my line of work as a healthcare worker, I certainly do, as we are required to do so to protect our patients and ensure that infection is not spread any farther. We are all-around lots of different people and we do not know if they’ve been vaccinated, so if you’re in doubt, get tested.

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