It's been another whiplash week in covid-land, with crushing numbers of hospitalizations and deaths juxtaposed against the first vaccine administrations to healthcare providers and a second vaccine granted Emergency Use Authorization by the FDA followed by a positive vote from the ACIP/CDC. Presumably we will see the Moderna vaccine shipped this week, along with ongoing distribution of the Pfizer vaccine. I won't spend any time detailing the basics of the Moderna vaccine; it is an mRNA vaccine very similar to the Pfizer vaccine and much detail is available at FDA and CDC websites. However, I did want to mention a few nuances.
First, evidence to date is insufficient to compare safety and efficacy of the two vaccines. The study findings were very similar, and given the minor differences in study design it would be improper to consider any head-to-head comparison at this time. Eventually we should know about any significant differences such as duration of immunity.
Note that a good deal of the discussion at the FDA/VRBPAC meeting concerned how to continue the ongoing Pfizer and Moderna trials: ethics and practical considerations of how to manage the placebo recipients in those trials who do have the ability to drop out of further follow up in the trials as well as seek their own antibody testing and immunization. The logistics of continuing a double-blinded crossover design trial (placebo recipients receive vaccine, vaccine recipients receive placebo) are large. Many have advocated continuing with an open-label trial where placebo recipients receive vaccine but agree to continue in some modified follow up within their study.
A few more details about side effects have emerged. As in the Pfizer study, a few people developed Bell's palsy in the Moderna trial, too few to determine if this is above expected rates in the general population or greater in vaccine versus placebo recipients. Also, as in the Pfizer trial a handful of women were pregnant in both groups. These pregnancies are being followed by study investigators.
Of interest are a few cases of facial swelling following vaccine, all in individuals who underwent cosmetic injections in lips and similar areas. Apparently this has been reported with other vaccines such as flu vaccine, as well as with natural viral infections. It appeared these reactions resolved with no permanent sequelae but again are being watched.
In the meantime, a few more healthcare providers have developed anaphylactic-like reactions that may be tied to the Pfizer vaccine, even though this wasn't seen in the clinical trials. Note that a far greater number of people have received vaccine in the past week, over 500,000 in the US, than received vaccine in the trials. Rare events sometimes are noted after approval of any drug or vaccine due to larger numbers of people receiving the product.
I'm hoping I will be called to receive my COVID-19 vaccine soon, but regardless of vaccine status remember we all must continue safe public health practices and promote them to our patients.
I wanted to give a quick update and some suggestions about the now-authorized vaccine. Unless you've been carefully avoiding all media notices, you know that the FDA published their Emergency Use Authorization for this vaccine late on December 11. I had attended the Advisory Committee on Immunization Practices (ACIP) meeting earlier that day, and because of the EUA coming through they moved their scheduled Sunday meeting to today (December 12) at 11 AM, which I also attended. The ACIP and CDC did comment about many of the special considerations (e.g. pregnant and breastfeeding women, immunocompromised individuals); ultimately the recommendations passed unanimously.
Many details will be evolving in terms of guidance, etc, but I did want to give front-line providers some useful links to peruse in the meantime.
First, all of the slide presentations for the 2 ACIP meetings are posted. I'd particularly recommend the session on Clinical Considerations from December 12, but recognize much is changing with guidance for certain situations including allergies and pregnancy.
Another extremely important resource is the Vaccination Communication Toolkit. This also is still an evolving resource, but I'd strongly recommend all providers start to become familiar with these tools. Know that educational videos for vaccine storage, administration, etc are in the works, as are fact sheets for the general public in several languages.
Next Steps? At this point, don't worry about your specific role in this entire process, except in helping your patients and families realize that the vaccine was approved after a very transparent and extensive review of data and that they will be notified when they or family members are eligible to receive vaccine based on the pre-established allocation plan. Vaccine is in very limited supply now, so very few individuals will be vaccinated next week.
Some of the public may be concerned about the rapidity with which this vaccine was studied and authorized, not to mention concerns with possible undue political pressures. I am completely satisfied that FDA and ACIP/CDC have been very thoughtful and transparent in all their proceedings. From my point of view there is only 1 difference for this vaccine's approval compared to other vaccines approved under "normal" circumstances, and that is the duration of immunity. We will know the answer to that question relatively soon, but I don't find anything about safety or efficacy that has been short-circuited by the EUA process.
Probably every day the next week we'll see new materials and information made available. Next Thursday the FDA will again meet, this time regarding EUA for the Moderna vaccine. ACIP/CDC has planned the same Friday and Saturday or Sunday discussion schedule if this vaccine moves forward from FDA.
I spent most of my day December 10 trying to catch as much of the FDA Center for Biologics Evaluation and Research (CBER) meeting of the Vaccines and Related Biological Products Advisory Committee (VRBPAC) discussion of the Pfizer/BioNTech COVID-19 vaccine. Although I had some interruptions and much multi-tasking, I was able to watch most of the proceedings, plus I did have a chance to review the detailed briefings from FDA and Pfizer as well as all of the presentation slides, posted online for everyone. Overall I came away feeling that we now have a very clear picture of the data, certainly enough to make decisions about this vaccine for the short term. Obviously they covered a ton of information, but I'll try to distill down to the essentials.
First, the overview and major take-home messages. As you may already know, this is a messenger RNA vaccine; the technology and science for making these vaccines has been around for quite a while and been tested in small numbers of humans for different purposes. However, this is the first mRNA vaccine to undergo widespread testing and presumably use in people. The cartoon below is from the Pfizer slides and I think shows you how this works. The modified mRNA is contained in lipid nanoparticles (LNP) and when injected ends up in cells where the mRNA instructs the cell to make the SARS-CoV-2 spike protein. The protein then triggers an inflammatory response such that the recipient makes antibody to the protein as well as memory T and B cells, then lies in wait to attack anything possessing the spike protein to enter the body.
In terms of safety, bottom line is that no serious concerns were raised in the 20,000+ individuals who received the vaccine (the other half of the subjects received saline placebo injections). Local side effects such as pain and swelling at the injection site occurred but nothing dramatic there. Systemic reactions like fatigue and chills were reported by a few percent of vaccine recipients; fever also occurred and usually of short duration. Side effects were more common after the second vaccine dose. Efficacy was as you have heard in news reports, in the mid-90s% range and much higher than I had hoped originally.
Now for the nuances and special populations. You've probably heard about the 2 vaccine recipients in England who may have experienced severe allergic reactions to the vaccine. Pfizer presented what little is known so far about this, and the best I can say is that it is still pretty murky. It didn't really sound like true anaphylaxis to me, but we'll just need to wait for more details, I'm hoping in the next few days. The current trial did not include individuals with severe allergy profiles, unlike the 2 British recipients this week.
A couple other caveats from the safety aspect. Regional lymphadenopathy occurred in 64 individuals in the vaccine group versus 6 in the control group, nothing worrisome but certainly plausible as an uncommon side effect. Bell's palsy occurred in 4 vaccine recipients versus none of the controls, but that level is within the rate of Bell's palsy that would be expected in the general population not receiving any vaccine, so difficult to know if any connection to the Pfizer vaccine.
The immune response to this vaccine is what is termed "Th-1 biased." That's a good thing, because in the past (e.g. an RSV vaccine trial in the 1970s), vaccines have the capability to produce an exaggerated immune response by the host when exposed to the virus. The immunology of that process is now understood, and a Th-1 biased immune profile protects against this. The few vaccine recipients in the Pfizer trial who did develop subsequent infection with SARS-CoV-2 did not show evidence of severe disease; in fact it was very mild.
In terms of special populations, the trial did not enroll immunocompromised individuals though this is planned for the future. They might need a different vaccine dose; this will take a while to figure out. Similarly, pregnant women were not enrolled. However, 23 women subsequently became pregnant, 12 in the vaccine group and 11 in the placebo group. The only known outcome so far is 2 women in the placebo group experienced a spontaneous abortion. The remainder of the pregnancies are still ongoing so we'll hear more about that later. In the meantime, the language of what to do about guidance for pregnant women will come from the FDA. My guess, and it's only that, is pregnancy will not be an absolute contraindication to vaccination and women will be directed to discuss individually with their physician to weigh benefits versus potential risks. In terms of racial and ethnic distribution, the study group included a little under 10% Black or African Americans (about 4000 total) and a little over 25% Hispanic/Latinx participants.
The final special group, the one this audience cares most about, is children. The bulk of the study participants were adults 18 years and older, with a small number of 16- and 17-year olds. Pfizer has begun enrolling younger subjects down to age 12 years, a total of 2000, but no data on that yet. If no problems in that population, they will move to the 5-11 year-old age group, perhaps around April 2021, but they may need to determine if vaccine dose should be different in this younger population. I was surprised that there was some hesitancy from VRBPAC voting members about recommending use of the vaccine for the 16-17 year age group but ultimately the panel voted to recommend authorizing the vaccine for ages 16 and older, with 17 votes in favor, 4 against, and 1 abstention.
Two other important caveats from the FDA meeting: first, extensive post-authorization tracking is planned and already in place. This is called pharmacovigilance and will use both existing and newer vaccine tracking measures. I am very reassured about the quality of this pharmacovigilance plan, and this is where we begin to get some idea of how long immunity from the vaccine will persist. Second is the tricky ethical issue of what to do about the placebo recipients from this trial. Should they all be offered vaccines, which would make some of the long-term follow-up more difficult to assess? It would be great to invite all the trial participants to participate in a "blind crossover" trial, where prior vaccine recipients receive 2 doses of placebo and prior placebo recipients get 2 doses of the vaccine, everyone still remaining blinded but now everyone has the benefit from the vaccine. However, the logistic difficulties of performing what is essentially a new clinical trial for 40,000+ people is significant.
Next steps for this vaccine include what we hope will be a statement the evening of December 11 from FDA regarding recommendation for emergency use authorization. ACIP/CDC meetings are scheduled the afternoons of December 11 and 13, culminating in a vote to decide on whether the data warrant a recommendation for going forward assuming FDA recommends authorization. Then, on December 17, FDA VRBPAC will meet to discuss the Moderna vaccine data, with meeting materials to be posted soon on the web link earlier in this post.
In closing, I need to answer the many questions I've received from friends and colleagues: if offered, will I choose to receive this vaccine? My answer is unquestionably yes. Although we don't have long-term follow up of recipients, most significant side effects from vaccines appear in the first 6 weeks after immunization, and we have lots of information about that time period. Of course we don't know about any extremely rare side effects, but we never have that information about new drugs or vaccines until they are in widespread use. I'm perhaps a bit biased ahead of time in favor of vaccination: my age and occupation puts me in a high-risk group, I'm very familiar with the FDA review process and know several of the reviewers (no, I don't have any inside information about what they are doing with this or any other vaccine), and it turns out one of the senior vice presidents at Pfizer who presented most of the clinical data is an old friend of mine. I don't think any of these potential biases is coloring my decision, however.
I know I'm in trouble when I first hear about an infectious disease problem through the lay press. In the case of this year's flu vaccine, it was NPR, about a week ago. It looks like it started turning up on some national news feeds a few days earlier, and the message was that estimates of vaccine efficacy from Australia (the southern hemisphere flu season is winding down) were around 10%.
As is my usual practice, I go to the source data, which in this instance wasn't easy since virtually none of the lay press announcements included a link to that source. I finally traced it back to an online publication from October 26, 2017, and I'm still wondering why it didn't make more a splash back then, rather than 6 weeks later.
Based on interim reports of flu activity in Australia through late September, investigators did determine vaccine efficacy to be 10% (95% confidence interval -16 to 31) for influenza A H3 strains for all age groups; A H3 are the most common strains circulating this season. They used a test-negative study design for flu-positive patients seeking medical attention in sentinel clinics, which is a standard approach for flu vaccine efficacy research. Overall vaccine efficacy against all subtypes of influenza A and B was a more respectable 33% (17 to 46). Efficacy against A H3 strains varied by age. Children under 15 years of age and adults 15-64 years experienced rates of about 15% efficacy, while adults 65 and older having essentially no efficacy for A H3 strains. These numbers, if true, are not unprecedented with A H3 strains and have resulted in heavier flu seasons in the past.
It's too early to tell whether these estimates will hold for Australia once all data are available, and of course it's still too early to make an estimate for the US. A season with lower vaccine efficacy can mean greater risk of serious outcomes in high-risk populations, and this risk will be even greater if news about the lower efficacy results in fewer people seeking immunization this year. For now, it's important to stress that everyone should be immunized for influenza.
At the Montgomery County Pediatric Society meeting on December 4, 2017, Dr. Stuart Taylor asked me a very thought-provoking question. During a discussion of the numerous mumps outbreaks on college campuses and elsewhere recently, he wondered whether the effort and expense of tracking cases and immunizing in special situations was worthwhile, considering that mumps is a relatively mild illness. He recalled being told some decades ago that the mumps vaccine was included with the measles and rubella vaccines, both of which protect against infections with very serious complications, more out of convenience than for a compelling public health benefit. That question sent me back to the medical literature, and I learned (or maybe re-learned) some interesting points. Bottom line: mumps isn't as mild as most pediatricians think.
I wanted to first find recent information on mumps in more industrialized countries, but that isn't as easy as it sounds. However, studies on mumps outbreaks primarily in adolescents in England in 2004-5 offer some sobering statistics. In the United Kingdom, MMR vaccine was introduced in 1988 as a single dose for children 12-15 months of age, followed by a recommendation in 1996 to add a second dose to the routine immunization schedule. The 2004-5 epidemic largely affected individuals who were born too early to be offered the initial vaccine, but also protected somewhat during their childhood by a high vaccination rate in younger children, such that they weren't as likely to be exposed to the wild virus. Yung et al mined various databases in England and Wales from 2002-2006 and estimated that mumps infection resulted in 2647 case-patients being hospitalized, or about 6% of all mumps cases. That alone certainly would justify universal mumps immunization programs. These investigators also estimated hospitalization rates for some of the mumps complications: 4.4% for orchitis, 0.35% for meningitis (note aseptic meningitis is very common in mumps, about 50%, but is very mild usually), and 0.33% for mumps pancreatitis.
Mumps also is a cause of hearing loss, sometimes severe. A recent Japanese study was able to locate and confirm 67 cases of mumps hearing loss. Only 15 of them had obvious clinical mumps infection by history, and over 90% of these cases had severe hearing loss, though this latter figure may be inflated due to ascertainment bias. It is important to note that Japan is an outlier among developed countries in how they immunize for measles, mumps, and rubella.
A few interesting references:
Hviid A, et al. Mumps. Lancet 2008; 371:932-44.
IASR. Mumps (infectious parotitis) in Japan, as of September 2016. IASR 2016; 37:185-6. Online at https://www.niid.go.jp/niid/en/index-e/865-iasr/6843-440te.html.
Morita S, et al. The clinical features and prognosis of mumps-associated hearing loss: a retrospective, multi-institutional investigation in Japan. Acta Oto-laryngol 2017; 137 (Suppl 565):S44-7.
Yung C, Ramsay M. Estimating true hospital morbidity of complications associated with mumps outbreak, England, 2004/5. Euro Surveill 2016; 21, online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4998425/.
Yung C-F, et al. Mumps complications and effects of mumps vaccination, England and Wales, 2002-2006. Emerg Infect Dis 2011; 17:661-7.
